251643991557 has 128 divisors (see below), whose sum is σ = 410542612480. Its totient is φ = 134134133760.

The previous prime is 251643991481. The next prime is 251643991559. The reversal of 251643991557 is 755199346152.

It is not a de Polignac number, because 251643991557 - 2⁷ = 251643991429 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 251643991497 and 251643991506.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (251643991559) by changing a digit.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 346139928 + ... + 346140654.

It is an arithmetic number, because the mean of its divisors is an integer number (3207364160).

Almost surely, 2^251643991557 is an apocalyptic number.

It is an amenable number.

251643991557 is a deficient number, since it is larger than the sum of its proper divisors (158898620923).

251643991557 is a wasteful number, since it uses less digits than its factorization.

251643991557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1011.

The product of its digits is 10206000, while the sum is 57.

The spelling of 251643991557 in words is "two hundred fifty-one billion, six hundred forty-three million, nine hundred ninety-one thousand, five hundred fifty-seven".