61531440 has 160 divisors (see below), whose sum is σ = 203129856. Its totient is φ = 15375360.

The previous prime is 61531439. The next prime is 61531451. The reversal of 61531440 is 4413516.

61531440 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×61531440² = 7572236216947200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 61531440.

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 31 ways as a sum of consecutive naturals, for example, 391842 + ... + 391998.

Almost surely, 2^61531440 is an apocalyptic number.

61531440 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 61531440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (101564928).

61531440 is an abundant number, since it is smaller than the sum of its proper divisors (141598416).

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

61531440 is a wasteful number, since it uses less digits than its factorization.

61531440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 267 (or 261 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 61531440 is about 7844.1978557403. The cubic root of 61531440 is about 394.7895904434.

Adding to 61531440 its reverse (4413516), we get a palindrome (65944956).

The spelling of 61531440 in words is "sixty-one million, five hundred thirty-one thousand, four hundred forty".