644774487780 has 24 divisors (see below), whose sum is σ = 1805368565952. Its totient is φ = 171939863392.

The previous prime is 644774487761. The next prime is 644774487787. The reversal of 644774487780 is 87784477446.

It is a super-2 number, since 2×644774487780² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (644774487787) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5373120672 + ... + 5373120791.

It is an arithmetic number, because the mean of its divisors is an integer number (75223690248).

Almost surely, 2^644774487780 is an apocalyptic number.

644774487780 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

644774487780 is an abundant number, since it is smaller than the sum of its proper divisors (1160594078172).

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

644774487780 is a wasteful number, since it uses less digits than its factorization.

644774487780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10746241475 (or 10746241473 counting only the distinct ones).

The product of its (nonzero) digits is 236027904, while the sum is 66.

The spelling of 644774487780 in words is "six hundred forty-four billion, seven hundred seventy-four million, four hundred eighty-seven thousand, seven hundred eighty".