21912728 has 16 divisors (see below), whose sum is σ = 43503480. Its totient is φ = 10311808.

The previous prime is 21912727. The next prime is 21912733. The reversal of 21912728 is 82721912.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21912694 and 21912703.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21912727) 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, 80426 + ... + 80697.

Almost surely, 2^21912728 is an apocalyptic number.

It is an amenable number.

21912728 is a deficient number, since it is larger than the sum of its proper divisors (21590752).

21912728 is a wasteful number, since it uses less digits than its factorization.

21912728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 161146 (or 161142 counting only the distinct ones).

The product of its digits is 4032, while the sum is 32.

The square root of 21912728 is about 4681.1032887558. The cubic root of 21912728 is about 279.8329275407.

The spelling of 21912728 in words is "twenty-one million, nine hundred twelve thousand, seven hundred twenty-eight".