261564211022251 has 4 divisors (see below), whose sum is σ = 261606405610000. Its totient is φ = 261522016434504.

The previous prime is 261564211022243. The next prime is 261564211022263. The reversal of 261564211022251 is 152220112465162.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 261564211022251 - 2³ = 261564211022243 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261564211422251) 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, 21097284576 + ... + 21097296973.

It is an arithmetic number, because the mean of its divisors is an integer number (65401601402500).

Almost surely, 2^{261564211022251} is an apocalyptic number.

261564211022251 is a deficient number, since it is larger than the sum of its proper divisors (42194587749).

261564211022251 is an equidigital number, since it uses as much as digits as its factorization.

261564211022251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42194587748.

The product of its (nonzero) digits is 115200, while the sum is 40.

The spelling of 261564211022251 in words is "two hundred sixty-one trillion, five hundred sixty-four billion, two hundred eleven million, twenty-two thousand, two hundred fifty-one".