644536423 has 2 divisors, whose sum is σ = 644536424. Its totient is φ = 644536422.

The previous prime is 644536363. The next prime is 644536439. The reversal of 644536423 is 324635446.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644536423 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644536463) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322268211 + 322268212.

It is an arithmetic number, because the mean of its divisors is an integer number (322268212).

Almost surely, 2^644536423 is an apocalyptic number.

644536423 is a deficient number, since it is larger than the sum of its proper divisors (1).

644536423 is an equidigital number, since it uses as much as digits as its factorization.

644536423 is an evil number, because the sum of its binary digits is even.

The product of its digits is 207360, while the sum is 37.

The square root of 644536423 is about 25387.7218946482. The cubic root of 644536423 is about 863.8052147024.

It can be divided in two parts, 64453 and 6423, that added together give a triangular number (70876 = T₃₇₆).

The spelling of 644536423 in words is "six hundred forty-four million, five hundred thirty-six thousand, four hundred twenty-three".