21365081 has 4 divisors (see below), whose sum is σ = 21376464. Its totient is φ = 21353700.

The previous prime is 21365077. The next prime is 21365087. The reversal of 21365081 is 18056312.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21365081 - 2² = 21365077 is a prime.

It is a super-2 number, since 2×21365081² = 912933372273122, which contains 22 as substring.

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 21365081.

It is not an unprimeable number, because it can be changed into a prime (21365087) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2135 + ... + 6876.

It is an arithmetic number, because the mean of its divisors is an integer number (5344116).

Almost surely, 2^21365081 is an apocalyptic number.

It is an amenable number.

21365081 is a deficient number, since it is larger than the sum of its proper divisors (11383).

21365081 is an equidigital number, since it uses as much as digits as its factorization.

21365081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11382.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 21365081 is about 4622.2376615661. The cubic root of 21365081 is about 277.4820203160.

The spelling of 21365081 in words is "twenty-one million, three hundred sixty-five thousand, eighty-one".