21678925 has 12 divisors (see below), whose sum is σ = 27146080. Its totient is φ = 17172720.

The previous prime is 21678911. The next prime is 21678941. The reversal of 21678925 is 52987612.

It is not a de Polignac number, because 21678925 - 2¹¹ = 21676877 is a prime.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1635 + ... + 6784.

Almost surely, 2^21678925 is an apocalyptic number.

21678925 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21678925 is a deficient number, since it is larger than the sum of its proper divisors (5467155).

21678925 is a wasteful number, since it uses less digits than its factorization.

21678925 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8532 (or 8527 counting only the distinct ones).

The product of its digits is 60480, while the sum is 40.

The square root of 21678925 is about 4656.0632512886. The cubic root of 21678925 is about 278.8341190086.

The spelling of 21678925 in words is "twenty-one million, six hundred seventy-eight thousand, nine hundred twenty-five".