644002991 has 2 divisors, whose sum is σ = 644002992. Its totient is φ = 644002990.

The previous prime is 644002981. The next prime is 644003011. The reversal of 644002991 is 199200446.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644002991 - 2⁶ = 644002927 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644002901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322001495 + 322001496.

It is an arithmetic number, because the mean of its divisors is an integer number (322001496).

Almost surely, 2^644002991 is an apocalyptic number.

644002991 is a deficient number, since it is larger than the sum of its proper divisors (1).

644002991 is an equidigital number, since it uses as much as digits as its factorization.

644002991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15552, while the sum is 35.

The square root of 644002991 is about 25377.2140117862. The cubic root of 644002991 is about 863.5668477652.

The spelling of 644002991 in words is "six hundred forty-four million, two thousand, nine hundred ninety-one".