661556157 has 16 divisors (see below), whose sum is σ = 891388608. Its totient is φ = 436400640.

The previous prime is 661556131. The next prime is 661556179. The reversal of 661556157 is 751655166.

It is not a de Polignac number, because 661556157 - 2¹⁰ = 661555133 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661557157) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 144333 + ... + 148845.

It is an arithmetic number, because the mean of its divisors is an integer number (55711788).

Almost surely, 2^661556157 is an apocalyptic number.

It is an amenable number.

661556157 is a deficient number, since it is larger than the sum of its proper divisors (229832451).

661556157 is a wasteful number, since it uses less digits than its factorization.

661556157 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5020.

The product of its digits is 189000, while the sum is 42.

The square root of 661556157 is about 25720.7339903044. The cubic root of 661556157 is about 871.3425157224.

Subtracting 661556157 from its reverse (751655166), we obtain a palindrome (90099009).

The spelling of 661556157 in words is "six hundred sixty-one million, five hundred fifty-six thousand, one hundred fifty-seven".