21311998 has 8 divisors (see below), whose sum is σ = 31997808. Its totient is φ = 10646064.

The previous prime is 21311987. The next prime is 21312001. The reversal of 21311998 is 89911312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

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, 1911 + ... + 6802.

It is an arithmetic number, because the mean of its divisors is an integer number (3999726).

Almost surely, 2^21311998 is an apocalyptic number.

21311998 is a deficient number, since it is larger than the sum of its proper divisors (10685810).

21311998 is a wasteful number, since it uses less digits than its factorization.

21311998 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9938.

The product of its digits is 3888, while the sum is 34.

The square root of 21311998 is about 4616.4919581864. The cubic root of 21311998 is about 277.2520220644.

The spelling of 21311998 in words is "twenty-one million, three hundred eleven thousand, nine hundred ninety-eight".