1251620650021 has 4 divisors (see below), whose sum is σ = 1430423600032. Its totient is φ = 1072817700012.

The previous prime is 1251620649997. The next prime is 1251620650037. The reversal of 1251620650021 is 1200560261521.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1251620650021 - 2¹⁷ = 1251620518949 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1251620650921) 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, 89401474995 + ... + 89401475008.

It is an arithmetic number, because the mean of its divisors is an integer number (357605900008).

Almost surely, 2^{1251620650021} is an apocalyptic number.

It is an amenable number.

1251620650021 is a deficient number, since it is larger than the sum of its proper divisors (178802950011).

1251620650021 is an equidigital number, since it uses as much as digits as its factorization.

1251620650021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 178802950010.

The product of its (nonzero) digits is 7200, while the sum is 31.

It can be divided in two parts, 1251620 and 650021, that added together give a square (1901641 = 1379²).

The spelling of 1251620650021 in words is "one trillion, two hundred fifty-one billion, six hundred twenty million, six hundred fifty thousand, twenty-one".