21998508 has 24 divisors (see below), whose sum is σ = 58662912. Its totient is φ = 6285264.

The previous prime is 21998503. The next prime is 21998531. The reversal of 21998508 is 80589912.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a self number, because there is not a number n which added to its sum of digits gives 21998508.

It is not an unprimeable number, because it can be changed into a prime (21998503) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 130860 + ... + 131027.

It is an arithmetic number, because the mean of its divisors is an integer number (2444288).

Almost surely, 2^21998508 is an apocalyptic number.

21998508 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21998508 is an abundant number, since it is smaller than the sum of its proper divisors (36664404).

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

21998508 is a wasteful number, since it uses less digits than its factorization.

21998508 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 261901 (or 261899 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 42.

The square root of 21998508 is about 4690.2567093924. The cubic root of 21998508 is about 280.1975986152.

The spelling of 21998508 in words is "twenty-one million, nine hundred ninety-eight thousand, five hundred eight".