21687436 has 36 divisors (see below), whose sum is σ = 41861232. Its totient is φ = 9811296.

The previous prime is 21687373. The next prime is 21687473. The reversal of 21687436 is 63478612.

It is a junction number, because it is equal to n+sod(n) for n = 21687395 and 21687404.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 32886 + ... + 33538.

It is an arithmetic number, because the mean of its divisors is an integer number (1162812).

Almost surely, 2^21687436 is an apocalyptic number.

It is an amenable number.

21687436 is a deficient number, since it is larger than the sum of its proper divisors (20173796).

21687436 is a wasteful number, since it uses less digits than its factorization.

21687436 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 718 (or 697 counting only the distinct ones).

The product of its digits is 48384, while the sum is 37.

The square root of 21687436 is about 4656.9771311442. The cubic root of 21687436 is about 278.8706037004.

It can be divided in two parts, 2168 and 7436, that added together give a square (9604 = 98²).

The spelling of 21687436 in words is "twenty-one million, six hundred eighty-seven thousand, four hundred thirty-six".