11971190781 has 36 divisors (see below), whose sum is σ = 20124667836. Its totient is φ = 6828476160.

The previous prime is 11971190753. The next prime is 11971190821. The reversal of 11971190781 is 18709117911.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 6325020900 + 5646169881 = 79530^2 + 75141^2 .

It is not a de Polignac number, because 11971190781 - 2⁶ = 11971190717 is a prime.

It is a super-2 number, since 2×11971190781² (a number of 21 digits) contains 22 as substring.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11971190731) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 304806 + ... + 341831.

It is an arithmetic number, because the mean of its divisors is an integer number (559018551).

Almost surely, 2^11971190781 is an apocalyptic number.

11971190781 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

11971190781 is a deficient number, since it is larger than the sum of its proper divisors (8153477055).

11971190781 is a wasteful number, since it uses less digits than its factorization.

11971190781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 646682 (or 646668 counting only the distinct ones).

The product of its (nonzero) digits is 31752, while the sum is 45.

The spelling of 11971190781 in words is "eleven billion, nine hundred seventy-one million, one hundred ninety thousand, seven hundred eighty-one".