1187891281 has 4 divisors (see below), whose sum is σ = 1239538752. Its totient is φ = 1136243812.

The previous prime is 1187891219. The next prime is 1187891291. The reversal of 1187891281 is 1821987811.

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 1187891281 - 2¹⁵ = 1187858513 is a prime.

It is a super-2 number, since 2×1187891281² = 2822171390951641922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1187891291) 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, 25823701 + ... + 25823746.

It is an arithmetic number, because the mean of its divisors is an integer number (309884688).

Almost surely, 2^1187891281 is an apocalyptic number.

It is an amenable number.

1187891281 is a deficient number, since it is larger than the sum of its proper divisors (51647471).

1187891281 is an equidigital number, since it uses as much as digits as its factorization.

1187891281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51647470.

The product of its digits is 64512, while the sum is 46.

The square root of 1187891281 is about 34465.7987140876. The cubic root of 1187891281 is about 1059.0721918731.

The spelling of 1187891281 in words is "one billion, one hundred eighty-seven million, eight hundred ninety-one thousand, two hundred eighty-one".