21716891 has 16 divisors (see below), whose sum is σ = 25681920. Its totient is φ = 17975520.

The previous prime is 21716887. The next prime is 21716927. The reversal of 21716891 is 19861712.

It is a cyclic number.

It is not a de Polignac number, because 21716891 - 2² = 21716887 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21716831) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 49250 + ... + 49688.

It is an arithmetic number, because the mean of its divisors is an integer number (1605120).

Almost surely, 2^21716891 is an apocalyptic number.

21716891 is a deficient number, since it is larger than the sum of its proper divisors (3965029).

21716891 is a wasteful number, since it uses less digits than its factorization.

21716891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 674.

The product of its digits is 6048, while the sum is 35.

The square root of 21716891 is about 4660.1385172546. The cubic root of 21716891 is about 278.9967968526.

The spelling of 21716891 in words is "twenty-one million, seven hundred sixteen thousand, eight hundred ninety-one".