621711991 has 2 divisors, whose sum is σ = 621711992. Its totient is φ = 621711990.

The previous prime is 621711989. The next prime is 621712001. The reversal of 621711991 is 199117126.

621711991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 621711991 - 2¹ = 621711989 is a prime.

Together with 621711989, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 621711991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (621711941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 310855995 + 310855996.

It is an arithmetic number, because the mean of its divisors is an integer number (310855996).

Almost surely, 2^621711991 is an apocalyptic number.

621711991 is a deficient number, since it is larger than the sum of its proper divisors (1).

621711991 is an equidigital number, since it uses as much as digits as its factorization.

621711991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6804, while the sum is 37.

The square root of 621711991 is about 24934.1531037250. The cubic root of 621711991 is about 853.4860254140.

The spelling of 621711991 in words is "six hundred twenty-one million, seven hundred eleven thousand, nine hundred ninety-one".