21391799 has 16 divisors (see below), whose sum is σ = 25280640. Its totient is φ = 17844960.

The previous prime is 21391793. The next prime is 21391801. The reversal of 21391799 is 99719312.

It is a cyclic number.

It is not a de Polignac number, because 21391799 - 2⁸ = 21391543 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21391793) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 32132 + ... + 32790.

It is an arithmetic number, because the mean of its divisors is an integer number (1580040).

Almost surely, 2^21391799 is an apocalyptic number.

21391799 is a deficient number, since it is larger than the sum of its proper divisors (3888841).

21391799 is a wasteful number, since it uses less digits than its factorization.

21391799 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 910.

The product of its digits is 30618, while the sum is 41.

The square root of 21391799 is about 4625.1269171775. The cubic root of 21391799 is about 277.5976400719.

The spelling of 21391799 in words is "twenty-one million, three hundred ninety-one thousand, seven hundred ninety-nine".