21604779 has 16 divisors (see below), whose sum is σ = 36579840. Its totient is φ = 12345480.

The previous prime is 21604747. The next prime is 21604783. The reversal of 21604779 is 97740612.

It is a happy number.

It is not a de Polignac number, because 21604779 - 2⁵ = 21604747 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21604379) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 56967 + ... + 57344.

It is an arithmetic number, because the mean of its divisors is an integer number (2286240).

Almost surely, 2^21604779 is an apocalyptic number.

21604779 is a deficient number, since it is larger than the sum of its proper divisors (14975061).

21604779 is a wasteful number, since it uses less digits than its factorization.

21604779 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 114327 (or 114321 counting only the distinct ones).

The product of its (nonzero) digits is 21168, while the sum is 36.

The square root of 21604779 is about 4648.0941255530. The cubic root of 21604779 is about 278.5158675328.

The spelling of 21604779 in words is "twenty-one million, six hundred four thousand, seven hundred seventy-nine".