21002681 has 8 divisors (see below), whose sum is σ = 24456384. Its totient is φ = 17662320.

The previous prime is 21002677. The next prime is 21002689. The reversal of 21002681 is 18620012.

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 21002681 - 2² = 21002677 is a prime.

It is a super-2 number, since 2×21002681² = 882225218375522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21002689) 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, 27935 + ... + 28676.

It is an arithmetic number, because the mean of its divisors is an integer number (3057048).

Almost surely, 2^21002681 is an apocalyptic number.

It is an amenable number.

21002681 is a deficient number, since it is larger than the sum of its proper divisors (3453703).

21002681 is an equidigital number, since it uses as much as digits as its factorization.

21002681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56671.

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 21002681 is about 4582.8682067020. The cubic root of 21002681 is about 275.9041578936.

Adding to 21002681 its reverse (18620012), we get a palindrome (39622693).

The spelling of 21002681 in words is "twenty-one million, two thousand, six hundred eighty-one".