21866436 has 30 divisors (see below), whose sum is σ = 57164030. Its totient is φ = 7288704.

The previous prime is 21866431. The next prime is 21866441. The reversal of 21866436 is 63466812.

21866436 is a `hidden beast` number, since 2 + 1 + 8 + 6 + 643 + 6 = 666.

It is an interprime number because it is at equal distance from previous prime (21866431) and next prime (21866441).

It can be written as a sum of positive squares in only one way, i.e., 11943936 + 9922500 = 3456^2 + 3150^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21866436.

It is not an unprimeable number, because it can be changed into a prime (21866431) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 33421 + ... + 34068.

Almost surely, 2^21866436 is an apocalyptic number.

It is an amenable number.

21866436 is an abundant number, since it is smaller than the sum of its proper divisors (35297594).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21866436 is a wasteful number, since it uses less digits than its factorization.

21866436 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67505 (or 67494 counting only the distinct ones).

The product of its digits is 41472, while the sum is 36.

The square root of 21866436 is about 4676.1561137327. The cubic root of 21866436 is about 279.6357337961.

The spelling of 21866436 in words is "twenty-one million, eight hundred sixty-six thousand, four hundred thirty-six".