21739881 has 8 divisors (see below), whose sum is σ = 29693664. Its totient is φ = 14139680.

The previous prime is 21739877. The next prime is 21739903. The reversal of 21739881 is 18893712.

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

It is a cyclic number.

It is not a de Polignac number, because 21739881 - 2² = 21739877 is a prime.

It is a super-2 number, since 2×21739881² = 945244851788322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21739801) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 88251 + ... + 88496.

It is an arithmetic number, because the mean of its divisors is an integer number (3711708).

Almost surely, 2^21739881 is an apocalyptic number.

It is an amenable number.

21739881 is a deficient number, since it is larger than the sum of its proper divisors (7953783).

21739881 is a wasteful number, since it uses less digits than its factorization.

21739881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 176791.

The product of its digits is 24192, while the sum is 39.

The square root of 21739881 is about 4662.6045296594. The cubic root of 21739881 is about 279.0952129397.

The spelling of 21739881 in words is "twenty-one million, seven hundred thirty-nine thousand, eight hundred eighty-one".