642931621 has 2 divisors, whose sum is σ = 642931622. Its totient is φ = 642931620.

The previous prime is 642931609. The next prime is 642931669. The reversal of 642931621 is 126139246.

It is a happy number.

642931621 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 can be written as a sum of positive squares in only one way, i.e., 351000225 + 291931396 = 18735^2 + 17086^2 .

It is a cyclic number.

It is not a de Polignac number, because 642931621 - 2⁵ = 642931589 is a prime.

It is a super-2 number, since 2×642931621² = 826722138563375282, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (642931691) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321465810 + 321465811.

It is an arithmetic number, because the mean of its divisors is an integer number (321465811).

Almost surely, 2^642931621 is an apocalyptic number.

It is an amenable number.

642931621 is a deficient number, since it is larger than the sum of its proper divisors (1).

642931621 is an equidigital number, since it uses as much as digits as its factorization.

642931621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15552, while the sum is 34.

The square root of 642931621 is about 25356.0963281022. The cubic root of 642931621 is about 863.0877023997.

The spelling of 642931621 in words is "six hundred forty-two million, nine hundred thirty-one thousand, six hundred twenty-one".