21998312 has 16 divisors (see below), whose sum is σ = 47139360. Its totient is φ = 9427824.

The previous prime is 21998309. The next prime is 21998321. The reversal of 21998312 is 21389912.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 196358 + ... + 196469.

It is an arithmetic number, because the mean of its divisors is an integer number (2946210).

Almost surely, 2^21998312 is an apocalyptic number.

It is an amenable number.

21998312 is an abundant number, since it is smaller than the sum of its proper divisors (25141048).

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

21998312 is a wasteful number, since it uses less digits than its factorization.

21998312 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 392840 (or 392836 counting only the distinct ones).

The product of its digits is 7776, while the sum is 35.

The square root of 21998312 is about 4690.2358149671. The cubic root of 21998312 is about 280.1967664544.

Subtracting from 21998312 its reverse (21389912), we obtain a square (608400 = 780²).

The spelling of 21998312 in words is "twenty-one million, nine hundred ninety-eight thousand, three hundred twelve".