21400865 has 4 divisors (see below), whose sum is σ = 25681044. Its totient is φ = 17120688.

The previous prime is 21400849. The next prime is 21400877. The reversal of 21400865 is 56800412.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9339136 + 12061729 = 3056^2 + 3473^2 .

It is a cyclic number.

It is not a de Polignac number, because 21400865 - 2⁴ = 21400849 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2140082 + ... + 2140091.

It is an arithmetic number, because the mean of its divisors is an integer number (6420261).

Almost surely, 2^21400865 is an apocalyptic number.

It is an amenable number.

21400865 is a deficient number, since it is larger than the sum of its proper divisors (4280179).

21400865 is an equidigital number, since it uses as much as digits as its factorization.

21400865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4280178.

The product of its (nonzero) digits is 1920, while the sum is 26.

The square root of 21400865 is about 4626.1068945713. The cubic root of 21400865 is about 277.6368504995.

The spelling of 21400865 in words is "twenty-one million, four hundred thousand, eight hundred sixty-five".