621856649 has 2 divisors, whose sum is σ = 621856650. Its totient is φ = 621856648.

The previous prime is 621856597. The next prime is 621856661. The reversal of 621856649 is 946658126.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 532686400 + 89170249 = 23080^2 + 9443^2 .

It is a cyclic number.

It is not a de Polignac number, because 621856649 - 2²⁰ = 620808073 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (621856679) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 310928324 + 310928325.

It is an arithmetic number, because the mean of its divisors is an integer number (310928325).

Almost surely, 2^621856649 is an apocalyptic number.

It is an amenable number.

621856649 is a deficient number, since it is larger than the sum of its proper divisors (1).

621856649 is an equidigital number, since it uses as much as digits as its factorization.

621856649 is an evil number, because the sum of its binary digits is even.

The product of its digits is 622080, while the sum is 47.

The square root of 621856649 is about 24937.0537353553. The cubic root of 621856649 is about 853.5522157662.

The spelling of 621856649 in words is "six hundred twenty-one million, eight hundred fifty-six thousand, six hundred forty-nine".