21713681 has 4 divisors (see below), whose sum is σ = 23687664. Its totient is φ = 19739700.

The previous prime is 21713677. The next prime is 21713683. The reversal of 21713681 is 18631712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21713681 - 2² = 21713677 is a prime.

It is a super-2 number, since 2×21713681² = 942967885139522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21713683) by changing a digit.

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 in 3 ways as a sum of consecutive naturals, for example, 986975 + ... + 986996.

It is an arithmetic number, because the mean of its divisors is an integer number (5921916).

Almost surely, 2^21713681 is an apocalyptic number.

It is an amenable number.

21713681 is a deficient number, since it is larger than the sum of its proper divisors (1973983).

21713681 is a wasteful number, since it uses less digits than its factorization.

21713681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1973982.

The product of its digits is 2016, while the sum is 29.

The square root of 21713681 is about 4659.7940941634. The cubic root of 21713681 is about 278.9830498903.

The spelling of 21713681 in words is "twenty-one million, seven hundred thirteen thousand, six hundred eighty-one".