20781212761 has 4 divisors (see below), whose sum is σ = 21223366272. Its totient is φ = 20339059252.

The previous prime is 20781212729. The next prime is 20781212773. The reversal of 20781212761 is 16721218702.

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.

It is a cyclic number.

It is not a de Polignac number, because 20781212761 - 2⁵ = 20781212729 is a prime.

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 20781212761.

It is not an unprimeable number, because it can be changed into a prime (20781212161) 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, 221076685 + ... + 221076778.

It is an arithmetic number, because the mean of its divisors is an integer number (5305841568).

Almost surely, 2^20781212761 is an apocalyptic number.

It is an amenable number.

20781212761 is a deficient number, since it is larger than the sum of its proper divisors (442153511).

20781212761 is an equidigital number, since it uses as much as digits as its factorization.

20781212761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 442153510.

The product of its (nonzero) digits is 18816, while the sum is 37.

The spelling of 20781212761 in words is "twenty billion, seven hundred eighty-one million, two hundred twelve thousand, seven hundred sixty-one".