21117718 has 4 divisors (see below), whose sum is σ = 31676580. Its totient is φ = 10558858.

The previous prime is 21117709. The next prime is 21117737. The reversal of 21117718 is 81771112.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5279428 + ... + 5279431.

It is an arithmetic number, because the mean of its divisors is an integer number (7919145).

Almost surely, 2^21117718 is an apocalyptic number.

21117718 is a deficient number, since it is larger than the sum of its proper divisors (10558862).

21117718 is a wasteful number, since it uses less digits than its factorization.

21117718 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10558861.

The product of its digits is 784, while the sum is 28.

The square root of 21117718 is about 4595.4018322667. The cubic root of 21117718 is about 276.4069732953.

The spelling of 21117718 in words is "twenty-one million, one hundred seventeen thousand, seven hundred eighteen".