21725 has 12 divisors (see below), whose sum is σ = 29760. Its totient is φ = 15600.

The previous prime is 21713. The next prime is 21727. The reversal of 21725 is 52712.

It is not a de Polignac number, because 21725 - 2⁶ = 21661 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21727) 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, 236 + ... + 314.

It is an arithmetic number, because the mean of its divisors is an integer number (2480).

2²¹⁷²⁵ is an apocalyptic number.

21725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21725 is a deficient number, since it is larger than the sum of its proper divisors (8035).

21725 is a wasteful number, since it uses less digits than its factorization.

21725 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 100 (or 95 counting only the distinct ones).

The product of its digits is 140, while the sum is 17.

The square root of 21725 is about 147.3940297298. The cubic root of 21725 is about 27.9031517960.

It can be divided in two parts, 217 and 25, that added together give a palindrome (242).

The spelling of 21725 in words is "twenty-one thousand, seven hundred twenty-five".