21987398 has 16 divisors (see below), whose sum is σ = 34703424. Its totient is φ = 10434240.

The previous prime is 21987373. The next prime is 21987403. The reversal of 21987398 is 89378912.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 590 + ... + 6657.

It is an arithmetic number, because the mean of its divisors is an integer number (2168964).

Almost surely, 2^21987398 is an apocalyptic number.

21987398 is a deficient number, since it is larger than the sum of its proper divisors (12716026).

21987398 is a wasteful number, since it uses less digits than its factorization.

21987398 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7327.

The product of its digits is 217728, while the sum is 47.

The square root of 21987398 is about 4689.0721896768. The cubic root of 21987398 is about 280.1504208775.

The spelling of 21987398 in words is "twenty-one million, nine hundred eighty-seven thousand, three hundred ninety-eight".