21681825 has 48 divisors (see below), whose sum is σ = 40122432. Its totient is φ = 10240000.

The previous prime is 21681799. The next prime is 21681833. The reversal of 21681825 is 52818612.

It is not a de Polignac number, because 21681825 - 2⁷ = 21681697 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 33505 + ... + 34145.

It is an arithmetic number, because the mean of its divisors is an integer number (835884).

Almost surely, 2^21681825 is an apocalyptic number.

21681825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21681825 is a deficient number, since it is larger than the sum of its proper divisors (18440607).

21681825 is a wasteful number, since it uses less digits than its factorization.

21681825 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 706 (or 701 counting only the distinct ones).

The product of its digits is 7680, while the sum is 33.

The square root of 21681825 is about 4656.3746627607. The cubic root of 21681825 is about 278.8465517114.

It can be divided in two parts, 2168 and 1825, that added together give a palindrome (3993).

The spelling of 21681825 in words is "twenty-one million, six hundred eighty-one thousand, eight hundred twenty-five".