20921700399 has 4 divisors (see below), whose sum is σ = 27895600536. Its totient is φ = 13947800264.

The previous prime is 20921700379. The next prime is 20921700433. The reversal of 20921700399 is 99300712902.

It is a happy number.

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 20921700399 - 2¹⁵ = 20921667631 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20921700399.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20921700379) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3486950064 + ... + 3486950069.

It is an arithmetic number, because the mean of its divisors is an integer number (6973900134).

Almost surely, 2^20921700399 is an apocalyptic number.

20921700399 is a deficient number, since it is larger than the sum of its proper divisors (6973900137).

20921700399 is an equidigital number, since it uses as much as digits as its factorization.

20921700399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6973900136.

The product of its (nonzero) digits is 61236, while the sum is 42.

The spelling of 20921700399 in words is "twenty billion, nine hundred twenty-one million, seven hundred thousand, three hundred ninety-nine".