661431537 has 12 divisors (see below), whose sum is σ = 1028893684. Its totient is φ = 407034720.

The previous prime is 661431509. The next prime is 661431559. The reversal of 661431537 is 735134166.

661431537 is a `hidden beast` number, since 6 + 614 + 3 + 1 + 5 + 37 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 33628401 + 627803136 = 5799^2 + 25056^2 .

It is not a de Polignac number, because 661431537 - 2¹⁵ = 661398769 is a prime.

It is not an unprimeable number, because it can be changed into a prime (661431577) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2826514 + ... + 2826747.

Almost surely, 2^661431537 is an apocalyptic number.

It is an amenable number.

661431537 is a deficient number, since it is larger than the sum of its proper divisors (367462147).

661431537 is a wasteful number, since it uses less digits than its factorization.

661431537 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5653280 (or 5653277 counting only the distinct ones).

The product of its digits is 45360, while the sum is 36.

The square root of 661431537 is about 25718.3113170364. The cubic root of 661431537 is about 871.2877995192.

The spelling of 661431537 in words is "six hundred sixty-one million, four hundred thirty-one thousand, five hundred thirty-seven".