644221337956 has 27 divisors (see below), whose sum is σ = 1311473456307. Its totient is φ = 276090043320.

The previous prime is 644221337953. The next prime is 644221337959. The reversal of 644221337956 is 659733122446.

The square root of 644221337956 is 802634.

It is a perfect power (a square), and thus also a powerful number.

644221337956 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (644221337953) and next prime (644221337959).

It is a super-2 number, since 2×644221337956² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (644221337953) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 11208211 + ... + 11265541.

Almost surely, 2^644221337956 is an apocalyptic number.

644221337956 is the 802634-th square number.

It is an amenable number.

644221337956 is an abundant number, since it is smaller than the sum of its proper divisors (667252118351).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644221337956 is an frugal number, since it uses more digits than its factorization.

644221337956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 114680 (or 57340 counting only the distinct ones).

The product of its digits is 6531840, while the sum is 52.

The spelling of 644221337956 in words is "six hundred forty-four billion, two hundred twenty-one million, three hundred thirty-seven thousand, nine hundred fifty-six".