21311518 has 8 divisors (see below), whose sum is σ = 32008680. Its totient is φ = 10641960.

The previous prime is 21311503. The next prime is 21311527. The reversal of 21311518 is 81511312.

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, 4848 + ... + 8131.

It is an arithmetic number, because the mean of its divisors is an integer number (4001085).

Almost surely, 2^21311518 is an apocalyptic number.

21311518 is a deficient number, since it is larger than the sum of its proper divisors (10697162).

21311518 is a wasteful number, since it uses less digits than its factorization.

21311518 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13802.

The product of its digits is 240, while the sum is 22.

The square root of 21311518 is about 4616.4399703668. The cubic root of 21311518 is about 277.2499405769.

The spelling of 21311518 in words is "twenty-one million, three hundred eleven thousand, five hundred eighteen".