644132081 has 4 divisors (see below), whose sum is σ = 645814272. Its totient is φ = 642449892.

The previous prime is 644132059. The next prime is 644132101. The reversal of 644132081 is 180231446.

644132081 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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.

It is a cyclic number.

It is not a de Polignac number, because 644132081 - 2¹⁰ = 644131057 is a prime.

It is a super-2 number, since 2×644132081² = 829812275546781122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644132051) 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, 840521 + ... + 841286.

It is an arithmetic number, because the mean of its divisors is an integer number (161453568).

Almost surely, 2^644132081 is an apocalyptic number.

It is an amenable number.

644132081 is a deficient number, since it is larger than the sum of its proper divisors (1682191).

644132081 is a wasteful number, since it uses less digits than its factorization.

644132081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1682190.

The product of its (nonzero) digits is 4608, while the sum is 29.

The square root of 644132081 is about 25379.7573077443. The cubic root of 644132081 is about 863.6245443899.

The spelling of 644132081 in words is "six hundred forty-four million, one hundred thirty-two thousand, eighty-one".