21904072 has 16 divisors (see below), whose sum is σ = 41478300. Its totient is φ = 10843200.

The previous prime is 21904061. The next prime is 21904081. The reversal of 21904072 is 27040912.

It can be written as a sum of positive squares in 2 ways, for example, as 21104836 + 799236 = 4594^2 + 894^2 .

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, 12747 + ... + 14362.

Almost surely, 2^21904072 is an apocalyptic number.

It is an amenable number.

21904072 is a deficient number, since it is larger than the sum of its proper divisors (19574228).

21904072 is a wasteful number, since it uses less digits than its factorization.

21904072 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27216 (or 27212 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 21904072 is about 4680.1786290696. The cubic root of 21904072 is about 279.7960760080.

Adding to 21904072 its reverse (27040912), we get a palindrome (48944984).

The spelling of 21904072 in words is "twenty-one million, nine hundred four thousand, seventy-two".