261656351652521 has 24 divisors (see below), whose sum is σ = 317719122416640. Its totient is φ = 214451650799232.

The previous prime is 261656351652517. The next prime is 261656351652617. The reversal of 261656351652521 is 125256153656162.

It is not a de Polignac number, because 261656351652521 - 2² = 261656351652517 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (261656351654521) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 36805961 + ... + 43335798.

It is an arithmetic number, because the mean of its divisors is an integer number (13238296767360).

Almost surely, 2^{261656351652521} is an apocalyptic number.

It is an amenable number.

261656351652521 is a deficient number, since it is larger than the sum of its proper divisors (56062770764119).

261656351652521 is a wasteful number, since it uses less digits than its factorization.

261656351652521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80144693 (or 80144686 counting only the distinct ones).

The product of its digits is 19440000, while the sum is 56.

The spelling of 261656351652521 in words is "two hundred sixty-one trillion, six hundred fifty-six billion, three hundred fifty-one million, six hundred fifty-two thousand, five hundred twenty-one".