21156408 has 96 divisors (see below), whose sum is σ = 70543200. Its totient is φ = 5577984.

The previous prime is 21156407. The next prime is 21156413. The reversal of 21156408 is 80465112.

21156408 is a `hidden beast` number, since 2 + 1 + 15 + 640 + 8 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21156403) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4938 + ... + 8166.

It is an arithmetic number, because the mean of its divisors is an integer number (734825).

Almost surely, 2^21156408 is an apocalyptic number.

21156408 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21156408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35271600).

21156408 is an abundant number, since it is smaller than the sum of its proper divisors (49386792).

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

21156408 is a wasteful number, since it uses less digits than its factorization.

21156408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3261 (or 3254 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 21156408 is about 4599.6095486465. The cubic root of 21156408 is about 276.5756730487.

The spelling of 21156408 in words is "twenty-one million, one hundred fifty-six thousand, four hundred eight".