21763891 has 16 divisors (see below), whose sum is σ = 23823360. Its totient is φ = 19827360.

The previous prime is 21763883. The next prime is 21763897. The reversal of 21763891 is 19836712.

It is a cyclic number.

It is not a de Polignac number, because 21763891 - 2³ = 21763883 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21763891.

It is not an unprimeable number, because it can be changed into a prime (21763897) 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, 38376 + ... + 38938.

It is an arithmetic number, because the mean of its divisors is an integer number (1488960).

Almost surely, 2^21763891 is an apocalyptic number.

21763891 is the 2494-th nonagonal number.

21763891 is a deficient number, since it is larger than the sum of its proper divisors (2059469).

21763891 is a wasteful number, since it uses less digits than its factorization.

21763891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 666.

The product of its digits is 18144, while the sum is 37.

The square root of 21763891 is about 4665.1785603554. The cubic root of 21763891 is about 279.1979214233.

The spelling of 21763891 in words is "twenty-one million, seven hundred sixty-three thousand, eight hundred ninety-one".