21978838 has 16 divisors (see below), whose sum is σ = 37785600. Its totient is φ = 9392616.

The previous prime is 21978799. The next prime is 21978871. The reversal of 21978838 is 83887912.

It is a congruent number.

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, 3313 + ... + 7411.

It is an arithmetic number, because the mean of its divisors is an integer number (2361600).

Almost surely, 2^21978838 is an apocalyptic number.

21978838 is a deficient number, since it is larger than the sum of its proper divisors (15806762).

21978838 is a wasteful number, since it uses less digits than its factorization.

21978838 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4491.

The product of its digits is 193536, while the sum is 46.

The square root of 21978838 is about 4688.1593402955. The cubic root of 21978838 is about 280.1140606728.

The spelling of 21978838 in words is "twenty-one million, nine hundred seventy-eight thousand, eight hundred thirty-eight".