21339681 has 12 divisors (see below), whose sum is σ = 31275216. Its totient is φ = 12932920.

The previous prime is 21339677. The next prime is 21339733. The reversal of 21339681 is 18693312.

It is not a de Polignac number, because 21339681 - 2² = 21339677 is a prime.

It is a super-2 number, since 2×21339681² = 910763970363522, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (21339671) 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 11 ways as a sum of consecutive naturals, for example, 29031 + ... + 29756.

It is an arithmetic number, because the mean of its divisors is an integer number (2606268).

Almost surely, 2^21339681 is an apocalyptic number.

It is an amenable number.

21339681 is a deficient number, since it is larger than the sum of its proper divisors (9935535).

21339681 is a wasteful number, since it uses less digits than its factorization.

21339681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58812 (or 58801 counting only the distinct ones).

The product of its digits is 7776, while the sum is 33.

The square root of 21339681 is about 4619.4892574829. The cubic root of 21339681 is about 277.3720146765.

The spelling of 21339681 in words is "twenty-one million, three hundred thirty-nine thousand, six hundred eighty-one".