21390799 has 4 divisors (see below), whose sum is σ = 21438064. Its totient is φ = 21343536.

The previous prime is 21390797. The next prime is 21390833. The reversal of 21390799 is 99709312.

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

It is a cyclic number.

It is not a de Polignac number, because 21390799 - 2¹ = 21390797 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21390791) 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, 22947 + ... + 23860.

It is an arithmetic number, because the mean of its divisors is an integer number (5359516).

Almost surely, 2^21390799 is an apocalyptic number.

21390799 is a deficient number, since it is larger than the sum of its proper divisors (47265).

21390799 is an equidigital number, since it uses as much as digits as its factorization.

21390799 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47264.

The product of its (nonzero) digits is 30618, while the sum is 40.

The square root of 21390799 is about 4625.0188107726. The cubic root of 21390799 is about 277.5933143960.

The spelling of 21390799 in words is "twenty-one million, three hundred ninety thousand, seven hundred ninety-nine".