656181557 has 4 divisors (see below), whose sum is σ = 677348736. Its totient is φ = 635014380.

The previous prime is 656181509. The next prime is 656181571. The reversal of 656181557 is 755181656.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 656181557 - 2¹⁸ = 655919413 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (656181157) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10583543 + ... + 10583604.

It is an arithmetic number, because the mean of its divisors is an integer number (169337184).

Almost surely, 2^656181557 is an apocalyptic number.

It is an amenable number.

656181557 is a deficient number, since it is larger than the sum of its proper divisors (21167179).

656181557 is a wasteful number, since it uses less digits than its factorization.

656181557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21167178.

The product of its digits is 252000, while the sum is 44.

The square root of 656181557 is about 25616.0410094925. The cubic root of 656181557 is about 868.9764494168.

Subtracting 656181557 from its reverse (755181656), we obtain a palindrome (99000099).

The spelling of 656181557 in words is "six hundred fifty-six million, one hundred eighty-one thousand, five hundred fifty-seven".