251042643261 has 12 divisors (see below), whose sum is σ = 365263993692. Its totient is φ = 166140142656.

The previous prime is 251042643223. The next prime is 251042643277. The reversal of 251042643261 is 162346240152.

251042643261 is a `hidden beast` number, since 2 + 5 + 1 + 0 + 4 + 2 + 643 + 2 + 6 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 170346878361 + 80695764900 = 412731^2 + 284070^2 .

It is not a de Polignac number, because 251042643261 - 2⁷ = 251042643133 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (251042643461) 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, 101800326 + ... + 101802791.

It is an arithmetic number, because the mean of its divisors is an integer number (30438666141).

Almost surely, 2^251042643261 is an apocalyptic number.

It is an amenable number.

251042643261 is a deficient number, since it is larger than the sum of its proper divisors (114221350431).

251042643261 is a wasteful number, since it uses less digits than its factorization.

251042643261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 203603260 (or 203603257 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 36.

The spelling of 251042643261 in words is "two hundred fifty-one billion, forty-two million, six hundred forty-three thousand, two hundred sixty-one".