20388721693 has 4 divisors (see below), whose sum is σ = 20693031040. Its totient is φ = 20084412348.

The previous prime is 20388721687. The next prime is 20388721747. The reversal of 20388721693 is 39612788302.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 39612788302 = 2 ⋅19806394151.

It is a cyclic number.

It is not a de Polignac number, because 20388721693 - 2⁹ = 20388721181 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 (20388721393) 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, 152154573 + ... + 152154706.

It is an arithmetic number, because the mean of its divisors is an integer number (5173257760).

Almost surely, 2^20388721693 is an apocalyptic number.

It is an amenable number.

20388721693 is a deficient number, since it is larger than the sum of its proper divisors (304309347).

20388721693 is an equidigital number, since it uses as much as digits as its factorization.

20388721693 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 304309346.

The product of its (nonzero) digits is 870912, while the sum is 49.

The spelling of 20388721693 in words is "twenty billion, three hundred eighty-eight million, seven hundred twenty-one thousand, six hundred ninety-three".