21399778771 has 6 divisors (see below), whose sum is σ = 24893620260. Its totient is φ = 18342667476.

The previous prime is 21399778723. The next prime is 21399778787. The reversal of 21399778771 is 17787799312.

It is not a de Polignac number, because 21399778771 - 2²⁵ = 21366224339 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21399778471) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 218365041 + ... + 218365138.

It is an arithmetic number, because the mean of its divisors is an integer number (4148936710).

Almost surely, 2^21399778771 is an apocalyptic number.

21399778771 is a deficient number, since it is larger than the sum of its proper divisors (3493841489).

21399778771 is an equidigital number, since it uses as much as digits as its factorization.

21399778771 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 436730193 (or 436730186 counting only the distinct ones).

The product of its digits is 9335088, while the sum is 61.

The spelling of 21399778771 in words is "twenty-one billion, three hundred ninety-nine million, seven hundred seventy-eight thousand, seven hundred seventy-one".