644020427 has 2 divisors, whose sum is σ = 644020428. Its totient is φ = 644020426.

The previous prime is 644020387. The next prime is 644020439. The reversal of 644020427 is 724020446.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644020427 - 2¹⁰ = 644019403 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 644020427.

It is not a weakly prime, because it can be changed into another prime (644020327) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322010213 + 322010214.

It is an arithmetic number, because the mean of its divisors is an integer number (322010214).

Almost surely, 2^644020427 is an apocalyptic number.

644020427 is a deficient number, since it is larger than the sum of its proper divisors (1).

644020427 is an equidigital number, since it uses as much as digits as its factorization.

644020427 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10752, while the sum is 29.

The square root of 644020427 is about 25377.5575459893. The cubic root of 644020427 is about 863.5746412154.

The spelling of 644020427 in words is "six hundred forty-four million, twenty thousand, four hundred twenty-seven".