644742031 has 2 divisors, whose sum is σ = 644742032. Its totient is φ = 644742030.

The previous prime is 644742011. The next prime is 644742037. The reversal of 644742031 is 130247446.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644742031 - 2¹¹ = 644739983 is a prime.

It is a super-2 number, since 2×644742031² = 831384573076009922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 644741984 and 644742002.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644742037) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322371015 + 322371016.

It is an arithmetic number, because the mean of its divisors is an integer number (322371016).

Almost surely, 2^644742031 is an apocalyptic number.

644742031 is a deficient number, since it is larger than the sum of its proper divisors (1).

644742031 is an equidigital number, since it uses as much as digits as its factorization.

644742031 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16128, while the sum is 31.

The square root of 644742031 is about 25391.7709307563. The cubic root of 644742031 is about 863.8970566186.

Adding to 644742031 its reverse (130247446), we get a palindrome (774989477).

The spelling of 644742031 in words is "six hundred forty-four million, seven hundred forty-two thousand, thirty-one".