646917391 has 2 divisors, whose sum is σ = 646917392. Its totient is φ = 646917390.

The previous prime is 646917329. The next prime is 646917407. The reversal of 646917391 is 193719646.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 646917391 - 2¹⁷ = 646786319 is a prime.

It is a super-2 number, since 2×646917391² = 837004221556493762, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (646915391) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323458695 + 323458696.

It is an arithmetic number, because the mean of its divisors is an integer number (323458696).

Almost surely, 2^646917391 is an apocalyptic number.

646917391 is a deficient number, since it is larger than the sum of its proper divisors (1).

646917391 is an equidigital number, since it uses as much as digits as its factorization.

646917391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 244944, while the sum is 46.

The square root of 646917391 is about 25434.5707846624. The cubic root of 646917391 is about 864.8675623361.

The spelling of 646917391 in words is "six hundred forty-six million, nine hundred seventeen thousand, three hundred ninety-one".