21520408 has 96 divisors (see below), whose sum is σ = 52284960. Its totient is φ = 8225280.

The previous prime is 21520399. The next prime is 21520423. The reversal of 21520408 is 80402512.

It is a hoax number, since the sum of its digits (22) coincides with the sum of the digits of its distinct prime factors.

It is a zygodrome in base 3.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 208885 + ... + 208987.

It is an arithmetic number, because the mean of its divisors is an integer number (544635).

Almost surely, 2^21520408 is an apocalyptic number.

21520408 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 21520408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26142480).

21520408 is an abundant number, since it is smaller than the sum of its proper divisors (30764552).

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

21520408 is a wasteful number, since it uses less digits than its factorization.

21520408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 177 (or 166 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 22.

The square root of 21520408 is about 4639.0093770114. The cubic root of 21520408 is about 278.1528410963.

The spelling of 21520408 in words is "twenty-one million, five hundred twenty thousand, four hundred eight".