20820756397 has 4 divisors (see below), whose sum is σ = 23795150176. Its totient is φ = 17846362620.

The previous prime is 20820756379. The next prime is 20820756401. The reversal of 20820756397 is 79365702802.

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: 79365702802 = 2 ⋅39682851401.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20820756397 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20820756397.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20820756367) 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, 1487196879 + ... + 1487196892.

It is an arithmetic number, because the mean of its divisors is an integer number (5948787544).

Almost surely, 2^20820756397 is an apocalyptic number.

It is an amenable number.

20820756397 is a deficient number, since it is larger than the sum of its proper divisors (2974393779).

20820756397 is an equidigital number, since it uses as much as digits as its factorization.

20820756397 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2974393778.

The product of its (nonzero) digits is 1270080, while the sum is 49.

The spelling of 20820756397 in words is "twenty billion, eight hundred twenty million, seven hundred fifty-six thousand, three hundred ninety-seven".