21684025 has 24 divisors (see below), whose sum is σ = 30355200. Its totient is φ = 15220800.

The previous prime is 21684023. The next prime is 21684029. The reversal of 21684025 is 52048612.

It is not a de Polignac number, because 21684025 - 2¹ = 21684023 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21683984 and 21684002.

It is not an unprimeable number, because it can be changed into a prime (21684023) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6616 + ... + 9334.

It is an arithmetic number, because the mean of its divisors is an integer number (1264800).

Almost surely, 2^21684025 is an apocalyptic number.

21684025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21684025 is a deficient number, since it is larger than the sum of its proper divisors (8671175).

21684025 is a wasteful number, since it uses less digits than its factorization.

21684025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2769 (or 2764 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 28.

The square root of 21684025 is about 4656.6108920544. The cubic root of 21684025 is about 278.8559826774.

The spelling of 21684025 in words is "twenty-one million, six hundred eighty-four thousand, twenty-five".