61557540 has 144 divisors (see below), whose sum is σ = 193945920. Its totient is φ = 14572800.

The previous prime is 61557533. The next prime is 61557547. The reversal of 61557540 is 4575516.

61557540 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (61557533) and next prime (61557547).

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61557547) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 442791 + ... + 442929.

Almost surely, 2^61557540 is an apocalyptic number.

61557540 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 61557540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (96972960).

61557540 is an abundant number, since it is smaller than the sum of its proper divisors (132388380).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

61557540 is a wasteful number, since it uses less digits than its factorization.

61557540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 234 (or 221 counting only the distinct ones).

The product of its (nonzero) digits is 21000, while the sum is 33.

The square root of 61557540 is about 7845.8613293889. The cubic root of 61557540 is about 394.8454023002.

It can be divided in two parts, 6155 and 7540, that added together give a triangular number (13695 = T₁₆₅).

The spelling of 61557540 in words is "sixty-one million, five hundred fifty-seven thousand, five hundred forty".