21578973 has 16 divisors (see below), whose sum is σ = 31080000. Its totient is φ = 13238784.

The previous prime is 21578971. The next prime is 21578981. The reversal of 21578973 is 37987512.

It is not a de Polignac number, because 21578973 - 2¹ = 21578971 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21578971) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16653 + ... + 17901.

It is an arithmetic number, because the mean of its divisors is an integer number (1942500).

Almost surely, 2^21578973 is an apocalyptic number.

It is an amenable number.

21578973 is a deficient number, since it is larger than the sum of its proper divisors (9501027).

21578973 is a wasteful number, since it uses less digits than its factorization.

21578973 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1708.

The product of its digits is 105840, while the sum is 42.

The square root of 21578973 is about 4645.3173196241. The cubic root of 21578973 is about 278.4049315210.

The spelling of 21578973 in words is "twenty-one million, five hundred seventy-eight thousand, nine hundred seventy-three".