21690836 has 6 divisors (see below), whose sum is σ = 37958970. Its totient is φ = 10845416.

The previous prime is 21690821. The next prime is 21690853. The reversal of 21690836 is 63809612.

It can be written as a sum of positive squares in only one way, i.e., 14899600 + 6791236 = 3860^2 + 2606^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21690796 and 21690805.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2711351 + ... + 2711358.

It is an arithmetic number, because the mean of its divisors is an integer number (6326495).

Almost surely, 2^21690836 is an apocalyptic number.

It is an amenable number.

21690836 is a deficient number, since it is larger than the sum of its proper divisors (16268134).

21690836 is a wasteful number, since it uses less digits than its factorization.

21690836 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5422713 (or 5422711 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 35.

The square root of 21690836 is about 4657.3421605031. The cubic root of 21690836 is about 278.8851760471.

The spelling of 21690836 in words is "twenty-one million, six hundred ninety thousand, eight hundred thirty-six".