251603561643 has 32 divisors (see below), whose sum is σ = 391629551616. Its totient is φ = 140687038848.

The previous prime is 251603561609. The next prime is 251603561663. The reversal of 251603561643 is 346165306152.

It is not a de Polignac number, because 251603561643 - 2⁸ = 251603561387 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 251603561595 and 251603561604.

It is not an unprimeable number, because it can be changed into a prime (251603561603) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 5715505 + ... + 5759357.

It is an arithmetic number, because the mean of its divisors is an integer number (12238423488).

Almost surely, 2^251603561643 is an apocalyptic number.

251603561643 is a deficient number, since it is larger than the sum of its proper divisors (140025989973).

251603561643 is a wasteful number, since it uses less digits than its factorization.

251603561643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49723.

The product of its (nonzero) digits is 388800, while the sum is 42.

Adding to 251603561643 its reverse (346165306152), we get a palindrome (597768867795).

The spelling of 251603561643 in words is "two hundred fifty-one billion, six hundred three million, five hundred sixty-one thousand, six hundred forty-three".