261621757161 has 12 divisors (see below), whose sum is σ = 394328445888. Its totient is φ = 166831265304.

The previous prime is 261621757141. The next prime is 261621757171. The reversal of 261621757161 is 161757126162.

261621757161 is a `hidden beast` number, since 2 + 6 + 1 + 6 + 2 + 17 + 571 + 61 = 666.

It is not a de Polignac number, because 261621757161 - 2²³ = 261613368553 is a prime.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (261621757141) 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, 631936405 + ... + 631936818.

It is an arithmetic number, because the mean of its divisors is an integer number (32860703824).

Almost surely, 2^261621757161 is an apocalyptic number.

It is an amenable number.

261621757161 is a deficient number, since it is larger than the sum of its proper divisors (132706688727).

261621757161 is a wasteful number, since it uses less digits than its factorization.

261621757161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1263873252 (or 1263873249 counting only the distinct ones).

The product of its digits is 211680, while the sum is 45.

The spelling of 261621757161 in words is "two hundred sixty-one billion, six hundred twenty-one million, seven hundred fifty-seven thousand, one hundred sixty-one".