21759408 has 160 divisors (see below), whose sum is σ = 72019200. Its totient is φ = 6220800.

The previous prime is 21759401. The next prime is 21759431. The reversal of 21759408 is 80495712.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (21759401) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 90168 + ... + 90408.

It is an arithmetic number, because the mean of its divisors is an integer number (450120).

Almost surely, 2^21759408 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21759408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36009600).

21759408 is an abundant number, since it is smaller than the sum of its proper divisors (50259792).

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

21759408 is a wasteful number, since it uses less digits than its factorization.

21759408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 288 (or 276 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The square root of 21759408 is about 4664.6980609681. The cubic root of 21759408 is about 279.1787500624.

The spelling of 21759408 in words is "twenty-one million, seven hundred fifty-nine thousand, four hundred eight".