644698069 has 2 divisors, whose sum is σ = 644698070. Its totient is φ = 644698068.

The previous prime is 644698057. The next prime is 644698079. The reversal of 644698069 is 960896446.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 526105969 + 118592100 = 22937^2 + 10890^2 .

It is a cyclic number.

It is not a de Polignac number, because 644698069 - 2⁷ = 644697941 is a prime.

It is a super-2 number, since 2×644698069² = 831271200344657522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644698009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322349034 + 322349035.

It is an arithmetic number, because the mean of its divisors is an integer number (322349035).

Almost surely, 2^644698069 is an apocalyptic number.

It is an amenable number.

644698069 is a deficient number, since it is larger than the sum of its proper divisors (1).

644698069 is an equidigital number, since it uses as much as digits as its factorization.

644698069 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2239488, while the sum is 52.

The square root of 644698069 is about 25390.9052418381. The cubic root of 644698069 is about 863.8774211139.

The spelling of 644698069 in words is "six hundred forty-four million, six hundred ninety-eight thousand, sixty-nine".