21691776771 has 48 divisors (see below), whose sum is σ = 36984482496. Its totient is φ = 11994697728.

The previous prime is 21691776763. The next prime is 21691776779. The reversal of 21691776771 is 17767719612.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21691776763) and next prime (21691776779).

It is not a de Polignac number, because 21691776771 - 2³ = 21691776763 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21691776779) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 199251 + ... + 288243.

It is an arithmetic number, because the mean of its divisors is an integer number (770510052).

Almost surely, 2^21691776771 is an apocalyptic number.

21691776771 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21691776771 is a deficient number, since it is larger than the sum of its proper divisors (15292705725).

21691776771 is a wasteful number, since it uses less digits than its factorization.

21691776771 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89132 (or 89129 counting only the distinct ones).

The product of its digits is 1555848, while the sum is 54.

The spelling of 21691776771 in words is "twenty-one billion, six hundred ninety-one million, seven hundred seventy-six thousand, seven hundred seventy-one".