21858636 has 12 divisors (see below), whose sum is σ = 51003512. Its totient is φ = 7286208.

The previous prime is 21858623. The next prime is 21858643. The reversal of 21858636 is 63685812.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (12).

It is a junction number, because it is equal to n+sod(n) for n = 21858594 and 21858603.

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, 910765 + ... + 910788.

Almost surely, 2^21858636 is an apocalyptic number.

It is an amenable number.

21858636 is an abundant number, since it is smaller than the sum of its proper divisors (29144876).

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

21858636 is a wasteful number, since it uses less digits than its factorization.

21858636 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1821560 (or 1821558 counting only the distinct ones).

The product of its digits is 69120, while the sum is 39.

The square root of 21858636 is about 4675.3220209949. The cubic root of 21858636 is about 279.6024801203.

The spelling of 21858636 in words is "twenty-one million, eight hundred fifty-eight thousand, six hundred thirty-six".