21264978 has 64 divisors (see below), whose sum is σ = 50948352. Its totient is φ = 5790720.

The previous prime is 21264959. The next prime is 21264979. The reversal of 21264978 is 87946212.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21264979) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 91150 + ... + 91382.

It is an arithmetic number, because the mean of its divisors is an integer number (796068).

Almost surely, 2^21264978 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21264978, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25474176).

21264978 is an abundant number, since it is smaller than the sum of its proper divisors (29683374).

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

21264978 is a wasteful number, since it uses less digits than its factorization.

21264978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 339.

The product of its digits is 48384, while the sum is 39.

The square root of 21264978 is about 4611.3965346736. The cubic root of 21264978 is about 277.0479744178.

The spelling of 21264978 in words is "twenty-one million, two hundred sixty-four thousand, nine hundred seventy-eight".