21356436 has 12 divisors (see below), whose sum is σ = 49831712. Its totient is φ = 7118808.

The previous prime is 21356431. The next prime is 21356453. The reversal of 21356436 is 63465312.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21356431) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 889840 + ... + 889863.

Almost surely, 2^21356436 is an apocalyptic number.

It is an amenable number.

21356436 is an abundant number, since it is smaller than the sum of its proper divisors (28475276).

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

21356436 is a wasteful number, since it uses less digits than its factorization.

21356436 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1779710 (or 1779708 counting only the distinct ones).

The product of its digits is 12960, while the sum is 30.

The square root of 21356436 is about 4621.3024138223. The cubic root of 21356436 is about 277.4445892123. Note that the first 3 decimals are identical.

The spelling of 21356436 in words is "twenty-one million, three hundred fifty-six thousand, four hundred thirty-six".