21978722 has 8 divisors (see below), whose sum is σ = 34907436. Its totient is φ = 10342912.

The previous prime is 21978701. The next prime is 21978743. The reversal of 21978722 is 22787912.

It is an interprime number because it is at equal distance from previous prime (21978701) and next prime (21978743).

It can be written as a sum of positive squares in 2 ways, for example, as 21631801 + 346921 = 4651^2 + 589^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 323183 + ... + 323250.

Almost surely, 2^21978722 is an apocalyptic number.

21978722 is a deficient number, since it is larger than the sum of its proper divisors (12928714).

21978722 is a wasteful number, since it uses less digits than its factorization.

21978722 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 646452.

The product of its digits is 28224, while the sum is 38.

The square root of 21978722 is about 4688.1469686860. The cubic root of 21978722 is about 280.1135678763.

The spelling of 21978722 in words is "twenty-one million, nine hundred seventy-eight thousand, seven hundred twenty-two".