21978244 has 12 divisors (see below), whose sum is σ = 38585484. Its totient is φ = 10953824.

The previous prime is 21978241. The next prime is 21978247. The reversal of 21978244 is 44287912.

It is an interprime number because it is at equal distance from previous prime (21978241) and next prime (21978247).

It can be written as a sum of positive squares in 2 ways, for example, as 1166400 + 20811844 = 1080^2 + 4562^2 .

It is not an unprimeable number, because it can be changed into a prime (21978241) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7399 + ... + 9934.

It is an arithmetic number, because the mean of its divisors is an integer number (3215457).

Almost surely, 2^21978244 is an apocalyptic number.

It is an amenable number.

21978244 is a deficient number, since it is larger than the sum of its proper divisors (16607240).

21978244 is a wasteful number, since it uses less digits than its factorization.

21978244 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17654 (or 17652 counting only the distinct ones).

The product of its digits is 32256, while the sum is 37.

The square root of 21978244 is about 4688.0959887784. The cubic root of 21978244 is about 280.1115371962. Note that the first 3 decimals are identical.

It can be divided in two parts, 21978 and 244, that added together give a palindrome (22222).

The spelling of 21978244 in words is "twenty-one million, nine hundred seventy-eight thousand, two hundred forty-four".