644606749722 has 32 divisors (see below), whose sum is σ = 1461456601920. Its totient is φ = 187901562240.

The previous prime is 644606749693. The next prime is 644606749799. The reversal of 644606749722 is 227947606446.

It is a super-2 number, since 2×644606749722² (a number of 24 digits) contains 22 as substring.

It is a Smith number, since the sum of its digits (57) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Harshad number since it is a multiple of its sum of digits (57).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 217477179 + ... + 217480142.

It is an arithmetic number, because the mean of its divisors is an integer number (45670518810).

Almost surely, 2^644606749722 is an apocalyptic number.

644606749722 is an abundant number, since it is smaller than the sum of its proper divisors (816849852198).

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

644606749722 is a wasteful number, since it uses less digits than its factorization.

644606749722 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 434957358.

The product of its (nonzero) digits is 24385536, while the sum is 57.

The spelling of 644606749722 in words is "six hundred forty-four billion, six hundred six million, seven hundred forty-nine thousand, seven hundred twenty-two".