21978930 has 16 divisors (see below), whose sum is σ = 52749504. Its totient is φ = 5861040.

The previous prime is 21978917. The next prime is 21978947. The reversal of 21978930 is 3987912.

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, 366286 + ... + 366345.

It is an arithmetic number, because the mean of its divisors is an integer number (3296844).

Almost surely, 2^21978930 is an apocalyptic number.

21978930 is an abundant number, since it is smaller than the sum of its proper divisors (30770574).

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

21978930 is a wasteful number, since it uses less digits than its factorization.

21978930 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 732641.

The product of its (nonzero) digits is 27216, while the sum is 39.

The square root of 21978930 is about 4688.1691522384. The cubic root of 21978930 is about 280.1144515103.

The spelling of 21978930 in words is "twenty-one million, nine hundred seventy-eight thousand, nine hundred thirty".