251642165170421 has 4 divisors (see below), whose sum is σ = 251723105078700. Its totient is φ = 251561225262144.

The previous prime is 251642165170351. The next prime is 251642165170471. The reversal of 251642165170421 is 124071561246152.

It is a happy number.

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 25138491268900 + 226503673901521 = 5013830^2 + 15050039^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-251642165170421 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (251642165170471) 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, 40469949476 + ... + 40469955693.

It is an arithmetic number, because the mean of its divisors is an integer number (62930776269675).

Almost surely, 2^{251642165170421} is an apocalyptic number.

It is an amenable number.

251642165170421 is a deficient number, since it is larger than the sum of its proper divisors (80939908279).

251642165170421 is an equidigital number, since it uses as much as digits as its factorization.

251642165170421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80939908278.

The product of its (nonzero) digits is 806400, while the sum is 47.

The spelling of 251642165170421 in words is "two hundred fifty-one trillion, six hundred forty-two billion, one hundred sixty-five million, one hundred seventy thousand, four hundred twenty-one".