61661640 has 64 divisors (see below), whose sum is σ = 187545600. Its totient is φ = 16215552.

The previous prime is 61661617. The next prime is 61661653. The reversal of 61661640 is 4616616.

61661640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 61661598 and 61661607.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 5241 + ... + 12279.

It is an arithmetic number, because the mean of its divisors is an integer number (2930400).

Almost surely, 2^61661640 is an apocalyptic number.

61661640 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 61661640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (93772800).

61661640 is an abundant number, since it is smaller than the sum of its proper divisors (125883960).

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

61661640 is a wasteful number, since it uses less digits than its factorization.

61661640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7126 (or 7122 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 30.

The square root of 61661640 is about 7852.4925978953. The cubic root of 61661640 is about 395.0678514002.

The spelling of 61661640 in words is "sixty-one million, six hundred sixty-one thousand, six hundred forty".