21891718 has 8 divisors (see below), whose sum is σ = 32969160. Its totient is φ = 10902000.

The previous prime is 21891691. The next prime is 21891719. The reversal of 21891718 is 81719812.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21891719) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21303 + ... + 22306.

It is an arithmetic number, because the mean of its divisors is an integer number (4121145).

Almost surely, 2^21891718 is an apocalyptic number.

21891718 is a deficient number, since it is larger than the sum of its proper divisors (11077442).

21891718 is a wasteful number, since it uses less digits than its factorization.

21891718 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43862.

The product of its digits is 8064, while the sum is 37.

The square root of 21891718 is about 4678.8586215016. The cubic root of 21891718 is about 279.7434640131.

The spelling of 21891718 in words is "twenty-one million, eight hundred ninety-one thousand, seven hundred eighteen".