21211043644 has 12 divisors (see below), whose sum is σ = 42422087344. Its totient is φ = 9090447264.

The previous prime is 21211043627. The next prime is 21211043653. The reversal of 21211043644 is 44634011212.

21211043644 is an admirable number.

It is a Harshad number since it is a multiple of its sum of digits (28), and also a Moran number because the ratio is a prime number: 757537273 = 21211043644 / (2 + 1 + 2 + 1 + 1 + 0 + 4 + 3 + 6 + 4 + 4).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 378768609 + ... + 378768664.

Almost surely, 2^21211043644 is an apocalyptic number.

It is an amenable number.

21211043644 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21211043644 is a wasteful number, since it uses less digits than its factorization.

21211043644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 757537284 (or 757537282 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 28.

Adding to 21211043644 its reverse (44634011212), we get a palindrome (65845054856).

The spelling of 21211043644 in words is "twenty-one billion, two hundred eleven million, forty-three thousand, six hundred forty-four".