21216836 has 12 divisors (see below), whose sum is σ = 38133228. Its totient is φ = 10321632.

The previous prime is 21216829. The next prime is 21216841. The reversal of 21216836 is 63861212.

It can be written as a sum of positive squares in 2 ways, for example, as 19096900 + 2119936 = 4370^2 + 1456^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21216799 and 21216808.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 71531 + ... + 71826.

It is an arithmetic number, because the mean of its divisors is an integer number (3177769).

Almost surely, 2^21216836 is an apocalyptic number.

It is an amenable number.

21216836 is a deficient number, since it is larger than the sum of its proper divisors (16916392).

21216836 is a wasteful number, since it uses less digits than its factorization.

21216836 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 143398 (or 143396 counting only the distinct ones).

The product of its digits is 3456, while the sum is 29.

The square root of 21216836 is about 4606.1736832212. The cubic root of 21216836 is about 276.8387458709.

The spelling of 21216836 in words is "twenty-one million, two hundred sixteen thousand, eight hundred thirty-six".