251221551320 has 64 divisors (see below), whose sum is σ = 570632040000. Its totient is φ = 99535318528.

The previous prime is 251221551319. The next prime is 251221551349. The reversal of 251221551320 is 23155122152.

It is a happy number.

It is a super-2 number, since 2×251221551320² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2080934 + ... + 2198346.

It is an arithmetic number, because the mean of its divisors is an integer number (8916125625).

Almost surely, 2^251221551320 is an apocalyptic number.

251221551320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

251221551320 is an abundant number, since it is smaller than the sum of its proper divisors (319410488680).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

251221551320 is a wasteful number, since it uses less digits than its factorization.

251221551320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 117932 (or 117928 counting only the distinct ones).

The product of its (nonzero) digits is 6000, while the sum is 29.

Adding to 251221551320 its reverse (23155122152), we get a palindrome (274376673472).

The spelling of 251221551320 in words is "two hundred fifty-one billion, two hundred twenty-one million, five hundred fifty-one thousand, three hundred twenty".