644266741 has 4 divisors (see below), whose sum is σ = 657974592. Its totient is φ = 630558892.

The previous prime is 644266739. The next prime is 644266759. The reversal of 644266741 is 147662446.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 147662446 = 2 ⋅73831223.

It is a cyclic number.

It is not a de Polignac number, because 644266741 - 2¹ = 644266739 is a prime.

It is a super-2 number, since 2×644266741² = 830159267117522162, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 644266694 and 644266703.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644264741) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6853855 + ... + 6853948.

It is an arithmetic number, because the mean of its divisors is an integer number (164493648).

Almost surely, 2^644266741 is an apocalyptic number.

It is an amenable number.

644266741 is a deficient number, since it is larger than the sum of its proper divisors (13707851).

644266741 is a wasteful number, since it uses less digits than its factorization.

644266741 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13707850.

The product of its digits is 193536, while the sum is 40.

The square root of 644266741 is about 25382.4100707557. The cubic root of 644266741 is about 863.6847223055.

The spelling of 644266741 in words is "six hundred forty-four million, two hundred sixty-six thousand, seven hundred forty-one".