21499440 has 80 divisors (see below), whose sum is σ = 68968800. Its totient is φ = 5533696.

The previous prime is 21499427. The next prime is 21499451. The reversal of 21499440 is 4499412.

It is a tau number, because it is divible by the number of its divisors (80).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5416 + ... + 8504.

It is an arithmetic number, because the mean of its divisors is an integer number (862110).

Almost surely, 2^21499440 is an apocalyptic number.

21499440 is a gapful number since it is divisible by the number (20) 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 21499440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34484400).

21499440 is an abundant number, since it is smaller than the sum of its proper divisors (47469360).

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

21499440 is a wasteful number, since it uses less digits than its factorization.

21499440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3134 (or 3128 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 33.

The square root of 21499440 is about 4636.7488610016. The cubic root of 21499440 is about 278.0624740983.

The spelling of 21499440 in words is "twenty-one million, four hundred ninety-nine thousand, four hundred forty".