21216925 has 12 divisors (see below), whose sum is σ = 27453600. Its totient is φ = 16235120.

The previous prime is 21216919. The next prime is 21216929. The reversal of 21216925 is 52961212.

It is not a de Polignac number, because 21216925 - 2⁹ = 21216413 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a junction number, because it is equal to n+sod(n) for n = 21216893 and 21216902.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21216929) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 17875 + ... + 19024.

It is an arithmetic number, because the mean of its divisors is an integer number (2287800).

Almost surely, 2^21216925 is an apocalyptic number.

21216925 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21216925 is a deficient number, since it is larger than the sum of its proper divisors (6236675).

21216925 is a wasteful number, since it uses less digits than its factorization.

21216925 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36932 (or 36927 counting only the distinct ones).

The product of its digits is 2160, while the sum is 28.

The square root of 21216925 is about 4606.1833441582. The cubic root of 21216925 is about 276.8391329631.

The spelling of 21216925 in words is "twenty-one million, two hundred sixteen thousand, nine hundred twenty-five".