261421716536557 has 4 divisors (see below), whose sum is σ = 261739361393440. Its totient is φ = 261104071679676.

The previous prime is 261421716536549. The next prime is 261421716536567. The reversal of 261421716536557 is 755635617124162.

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 261421716536557 - 2³ = 261421716536549 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 261421716536495 and 261421716536504.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261421716536507) 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, 158822427207 + ... + 158822428852.

It is an arithmetic number, because the mean of its divisors is an integer number (65434840348360).

Almost surely, 2^{261421716536557} is an apocalyptic number.

It is an amenable number.

261421716536557 is a deficient number, since it is larger than the sum of its proper divisors (317644856883).

261421716536557 is an equidigital number, since it uses as much as digits as its factorization.

261421716536557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 317644856882.

The product of its digits is 63504000, while the sum is 61.

The spelling of 261421716536557 in words is "two hundred sixty-one trillion, four hundred twenty-one billion, seven hundred sixteen million, five hundred thirty-six thousand, five hundred fifty-seven".