21281836 has 12 divisors (see below), whose sum is σ = 37753912. Its totient is φ = 10495008.

The previous prime is 21281797. The next prime is 21281891. The reversal of 21281836 is 63818212.

It is a super-3 number, since 3×21281836³ (a number of 23 digits) contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21281798 and 21281807.

It is an unprimeable number.

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, 36150 + ... + 36733.

Almost surely, 2^21281836 is an apocalyptic number.

It is an amenable number.

21281836 is a deficient number, since it is larger than the sum of its proper divisors (16472076).

21281836 is a wasteful number, since it uses less digits than its factorization.

21281836 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72960 (or 72958 counting only the distinct ones).

The product of its digits is 4608, while the sum is 31.

The square root of 21281836 is about 4613.2240353141. The cubic root of 21281836 is about 277.1211658268.

The spelling of 21281836 in words is "twenty-one million, two hundred eighty-one thousand, eight hundred thirty-six".