21644402 has 8 divisors (see below), whose sum is σ = 34964076. Its totient is φ = 9989712.

The previous prime is 21644387. The next prime is 21644407. The reversal of 21644402 is 20444612.

It can be written as a sum of positive squares in 2 ways, for example, as 17648401 + 3996001 = 4201^2 + 1999^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21644407) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 416213 + ... + 416264.

Almost surely, 2^21644402 is an apocalyptic number.

21644402 is a deficient number, since it is larger than the sum of its proper divisors (13319674).

21644402 is a wasteful number, since it uses less digits than its factorization.

21644402 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 832492.

The product of its (nonzero) digits is 1536, while the sum is 23.

The square root of 21644402 is about 4652.3544576913. The cubic root of 21644402 is about 278.6860288763.

The spelling of 21644402 in words is "twenty-one million, six hundred forty-four thousand, four hundred two".