20815999399 has 8 divisors (see below), whose sum is σ = 22427436752. Its totient is φ = 19206020160.

The previous prime is 20815999363. The next prime is 20815999409. The reversal of 20815999399 is 99399951802.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20815999399 - 2⁹ = 20815998887 is a prime.

It is a super-2 number, since 2×20815999399² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20815999399.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20815993399) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 334782 + ... + 392059.

It is an arithmetic number, because the mean of its divisors is an integer number (2803429594).

Almost surely, 2^20815999399 is an apocalyptic number.

20815999399 is a deficient number, since it is larger than the sum of its proper divisors (1611437353).

20815999399 is a wasteful number, since it uses less digits than its factorization.

20815999399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 729057.

The product of its (nonzero) digits is 14171760, while the sum is 64.

The spelling of 20815999399 in words is "twenty billion, eight hundred fifteen million, nine hundred ninety-nine thousand, three hundred ninety-nine".