21921125 has 16 divisors (see below), whose sum is σ = 27556464. Its totient is φ = 17409600.

The previous prime is 21921121. The next prime is 21921167. The reversal of 21921125 is 52112912.

It is a Cunningham number, because it is equal to 4682²+1.

It can be written as a sum of positive squares in 8 ways, for example, as 15499969 + 6421156 = 3937^2 + 2534^2 .

It is not a de Polignac number, because 21921125 - 2² = 21921121 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21921125.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21921121) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19067 + ... + 20183.

It is an arithmetic number, because the mean of its divisors is an integer number (1722279).

Almost surely, 2^21921125 is an apocalyptic number.

21921125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21921125 is a deficient number, since it is larger than the sum of its proper divisors (5635339).

21921125 is a wasteful number, since it uses less digits than its factorization.

21921125 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1289 (or 1279 counting only the distinct ones).

The product of its digits is 360, while the sum is 23.

The square root of 21921125 is about 4682.0001067920. Note that the first 3 decimals coincide. The cubic root of 21921125 is about 279.8686671500.

The spelling of 21921125 in words is "twenty-one million, nine hundred twenty-one thousand, one hundred twenty-five".