21149767791 has 8 divisors (see below), whose sum is σ = 31332989360. Its totient is φ = 14099845176.

The previous prime is 21149767721. The next prime is 21149767799. The reversal of 21149767791 is 19776794112.

It is a happy number.

21149767791 is a `hidden beast` number, since 2 + 1 + 1 + 497 + 67 + 7 + 91 = 666.

It is not a de Polignac number, because 21149767791 - 2¹⁰ = 21149766767 is a prime.

It is a super-2 number, since 2×21149767791² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21149767799) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 391662340 + ... + 391662393.

It is an arithmetic number, because the mean of its divisors is an integer number (3916623670).

Almost surely, 2^21149767791 is an apocalyptic number.

21149767791 is a deficient number, since it is larger than the sum of its proper divisors (10183221569).

21149767791 is an equidigital number, since it uses as much as digits as its factorization.

21149767791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 783324742 (or 783324736 counting only the distinct ones).

The product of its digits is 1333584, while the sum is 54.

The spelling of 21149767791 in words is "twenty-one billion, one hundred forty-nine million, seven hundred sixty-seven thousand, seven hundred ninety-one".