644401970 has 16 divisors (see below), whose sum is σ = 1160256960. Its totient is φ = 257686704.

The previous prime is 644401939. The next prime is 644401981. The reversal of 644401970 is 79104446.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 644401970.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 39491 + ... + 53369.

It is an arithmetic number, because the mean of its divisors is an integer number (72516060).

Almost surely, 2^644401970 is an apocalyptic number.

644401970 is a deficient number, since it is larger than the sum of its proper divisors (515854990).

644401970 is a wasteful number, since it uses less digits than its factorization.

644401970 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18529.

The product of its (nonzero) digits is 24192, while the sum is 35.

The square root of 644401970 is about 25385.0737639267. The cubic root of 644401970 is about 863.7451460623.

The spelling of 644401970 in words is "six hundred forty-four million, four hundred one thousand, nine hundred seventy".