21808936 has 16 divisors (see below), whose sum is σ = 40952340. Its totient is φ = 10888320.

The previous prime is 21808933. The next prime is 21808939. The reversal of 21808936 is 63980812.

It is an interprime number because it is at equal distance from previous prime (21808933) and next prime (21808939).

It can be written as a sum of positive squares in 2 ways, for example, as 21808900 + 36 = 4670^2 + 6^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21808895 and 21808904.

It is not an unprimeable number, because it can be changed into a prime (21808933) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5266 + ... + 8446.

Almost surely, 2^21808936 is an apocalyptic number.

It is an amenable number.

21808936 is a deficient number, since it is larger than the sum of its proper divisors (19143404).

21808936 is a wasteful number, since it uses less digits than its factorization.

21808936 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4044 (or 4040 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 21808936 is about 4670.0038543881. The cubic root of 21808936 is about 279.3904085078.

It can be divided in two parts, 218089 and 36, that multiplied together give a square (7851204 = 2802²).

The spelling of 21808936 in words is "twenty-one million, eight hundred eight thousand, nine hundred thirty-six".