2151591681 has 4 divisors (see below), whose sum is σ = 2868788912. Its totient is φ = 1434394452.

The previous prime is 2151591671. The next prime is 2151591697. The reversal of 2151591681 is 1861951512.

It is a happy number.

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 not a de Polignac number, because 2151591681 - 2¹⁹ = 2151067393 is a prime.

It is a super-2 number, since 2×2151591681² = 9258693523496811522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2151591641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 358598611 + ... + 358598616.

It is an arithmetic number, because the mean of its divisors is an integer number (717197228).

Almost surely, 2^2151591681 is an apocalyptic number.

It is an amenable number.

2151591681 is a deficient number, since it is larger than the sum of its proper divisors (717197231).

2151591681 is an equidigital number, since it uses as much as digits as its factorization.

2151591681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 717197230.

The product of its digits is 21600, while the sum is 39.

The square root of 2151591681 is about 46385.2528396688. The cubic root of 2151591681 is about 1290.9813018900.

The spelling of 2151591681 in words is "two billion, one hundred fifty-one million, five hundred ninety-one thousand, six hundred eighty-one".