251351440221 has 24 divisors (see below), whose sum is σ = 393711149664. Its totient is φ = 142207312800.

The previous prime is 251351440181. The next prime is 251351440289. The reversal of 251351440221 is 122044153152.

It is not a de Polignac number, because 251351440221 - 2¹⁴ = 251351423837 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (251351440621) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 8449875 + ... + 8479568.

It is an arithmetic number, because the mean of its divisors is an integer number (16404631236).

Almost surely, 2^251351440221 is an apocalyptic number.

251351440221 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

251351440221 is a deficient number, since it is larger than the sum of its proper divisors (142359709443).

251351440221 is a wasteful number, since it uses less digits than its factorization.

251351440221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16929561 (or 16929554 counting only the distinct ones).

The product of its (nonzero) digits is 9600, while the sum is 30.

Adding to 251351440221 its reverse (122044153152), we get a palindrome (373395593373).

The spelling of 251351440221 in words is "two hundred fifty-one billion, three hundred fifty-one million, four hundred forty thousand, two hundred twenty-one".