251461010021 has 4 divisors (see below), whose sum is σ = 270804164652. Its totient is φ = 232117855392.

The previous prime is 251461009999. The next prime is 251461010033. The reversal of 251461010021 is 120010164152.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 119484292225 + 131976717796 = 345665^2 + 363286^2 .

It is a cyclic number.

It is not a de Polignac number, because 251461010021 - 2²² = 251456815717 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (251461010321) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9671577296 + ... + 9671577321.

It is an arithmetic number, because the mean of its divisors is an integer number (67701041163).

Almost surely, 2^251461010021 is an apocalyptic number.

It is an amenable number.

251461010021 is a deficient number, since it is larger than the sum of its proper divisors (19343154631).

251461010021 is a wasteful number, since it uses less digits than its factorization.

251461010021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19343154630.

The product of its (nonzero) digits is 480, while the sum is 23.

Adding to 251461010021 its reverse (120010164152), we get a palindrome (371471174173).

The spelling of 251461010021 in words is "two hundred fifty-one billion, four hundred sixty-one million, ten thousand, twenty-one".