251620666354021 has 4 divisors (see below), whose sum is σ = 251620992852012. Its totient is φ = 251620339856032.

The previous prime is 251620666353997. The next prime is 251620666354039. The reversal of 251620666354021 is 120453666026152.

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 232916892408225 + 18703773945796 = 15261615^2 + 4324786^2 .

It is a cyclic number.

It is not a de Polignac number, because 251620666354021 - 2¹¹ = 251620666351973 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 (251620666354051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 162090256 + ... + 163635241.

It is an arithmetic number, because the mean of its divisors is an integer number (62905248213003).

Almost surely, 2^{251620666354021} is an apocalyptic number.

It is an amenable number.

251620666354021 is a deficient number, since it is larger than the sum of its proper divisors (326497991).

251620666354021 is an equidigital number, since it uses as much as digits as its factorization.

251620666354021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 326497990.

The product of its (nonzero) digits is 3110400, while the sum is 49.

The spelling of 251620666354021 in words is "two hundred fifty-one trillion, six hundred twenty billion, six hundred sixty-six million, three hundred fifty-four thousand, twenty-one".