661537504 has 24 divisors (see below), whose sum is σ = 1337604408. Its totient is φ = 321828480.

The previous prime is 661537469. The next prime is 661537511. The reversal of 661537504 is 405735166.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 278182 + ... + 280549.

It is an arithmetic number, because the mean of its divisors is an integer number (55733517).

Almost surely, 2^661537504 is an apocalyptic number.

It is an amenable number.

661537504 is an abundant number, since it is smaller than the sum of its proper divisors (676066904).

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

661537504 is a wasteful number, since it uses less digits than its factorization.

661537504 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 558778 (or 558770 counting only the distinct ones).

The product of its (nonzero) digits is 75600, while the sum is 37.

The square root of 661537504 is about 25720.3713814556. The cubic root of 661537504 is about 871.3343262918.

The spelling of 661537504 in words is "six hundred sixty-one million, five hundred thirty-seven thousand, five hundred four".