1644664901 has 16 divisors (see below), whose sum is σ = 1807930368. Its totient is φ = 1483732800.

The previous prime is 1644664891. The next prime is 1644664913. The reversal of 1644664901 is 1094664461.

It is a happy number.

It is not a de Polignac number, because 1644664901 - 2¹⁴ = 1644648517 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1644664951) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1287275 + ... + 1288551.

It is an arithmetic number, because the mean of its divisors is an integer number (112995648).

Almost surely, 2^1644664901 is an apocalyptic number.

1644664901 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1644664901 is a deficient number, since it is larger than the sum of its proper divisors (163265467).

1644664901 is a wasteful number, since it uses less digits than its factorization.

1644664901 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2092.

The product of its (nonzero) digits is 124416, while the sum is 41.

The square root of 1644664901 is about 40554.4683234782. The cubic root of 1644664901 is about 1180.3907785967.

The spelling of 1644664901 in words is "one billion, six hundred forty-four million, six hundred sixty-four thousand, nine hundred one".