1881156721 has 4 divisors (see below), whose sum is σ = 1881737200. Its totient is φ = 1880576244.

The previous prime is 1881156713. The next prime is 1881156763. The reversal of 1881156721 is 1276511881.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1276511881 = 719 ⋅1775399.

It is a cyclic number.

It is not a de Polignac number, because 1881156721 - 2³ = 1881156713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1881150721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 285351 + ... + 291868.

It is an arithmetic number, because the mean of its divisors is an integer number (470434300).

Almost surely, 2^1881156721 is an apocalyptic number.

It is an amenable number.

1881156721 is a deficient number, since it is larger than the sum of its proper divisors (580479).

1881156721 is an equidigital number, since it uses as much as digits as its factorization.

1881156721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 580478.

The product of its digits is 26880, while the sum is 40.

The square root of 1881156721 is about 43372.3036164786. The cubic root of 1881156721 is about 1234.4542319070.

The spelling of 1881156721 in words is "one billion, eight hundred eighty-one million, one hundred fifty-six thousand, seven hundred twenty-one".