621613921 has 2 divisors, whose sum is σ = 621613922. Its totient is φ = 621613920.

The previous prime is 621613919. The next prime is 621613933. The reversal of 621613921 is 129316126.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 620259025 + 1354896 = 24905^2 + 1164^2 .

It is a cyclic number.

It is not a de Polignac number, because 621613921 - 2¹ = 621613919 is a prime.

Together with 621613919, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (621613981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 310806960 + 310806961.

It is an arithmetic number, because the mean of its divisors is an integer number (310806961).

Almost surely, 2^621613921 is an apocalyptic number.

It is an amenable number.

621613921 is a deficient number, since it is larger than the sum of its proper divisors (1).

621613921 is an equidigital number, since it uses as much as digits as its factorization.

621613921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3888, while the sum is 31.

The square root of 621613921 is about 24932.1864464391. The cubic root of 621613921 is about 853.4411462325.

The spelling of 621613921 in words is "six hundred twenty-one million, six hundred thirteen thousand, nine hundred twenty-one".