21499840 has 28 divisors (see below), whose sum is σ = 51197256. Its totient is φ = 8599808.

The previous prime is 21499837. The next prime is 21499843. The reversal of 21499840 is 4899412.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21499837) and next prime (21499843).

It is a self number, because there is not a number n which added to its sum of digits gives 21499840.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21499843) 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, 33274 + ... + 33913.

Almost surely, 2^21499840 is an apocalyptic number.

21499840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21499840 is an abundant number, since it is smaller than the sum of its proper divisors (29697416).

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

21499840 is an equidigital number, since it uses as much as digits as its factorization.

21499840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67204 (or 67194 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 21499840 is about 4636.7919944720. The cubic root of 21499840 is about 278.0641985510.

The spelling of 21499840 in words is "twenty-one million, four hundred ninety-nine thousand, eight hundred forty".