20642399 has 4 divisors (see below), whose sum is σ = 20651880. Its totient is φ = 20632920.

The previous prime is 20642371. The next prime is 20642423. The reversal of 20642399 is 99324602.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20642399 is a prime.

It is a super-2 number, since 2×20642399² = 852217272950402, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20642359) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 344 + ... + 6434.

It is an arithmetic number, because the mean of its divisors is an integer number (5162970).

Almost surely, 2^20642399 is an apocalyptic number.

20642399 is a deficient number, since it is larger than the sum of its proper divisors (9481).

20642399 is an equidigital number, since it uses as much as digits as its factorization.

20642399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9480.

The product of its (nonzero) digits is 23328, while the sum is 35.

The square root of 20642399 is about 4543.3906941842. The cubic root of 20642399 is about 274.3174212194.

The spelling of 20642399 in words is "twenty million, six hundred forty-two thousand, three hundred ninety-nine".