1855791721 has 32 divisors (see below), whose sum is σ = 2240587008. Its totient is φ = 1503774720.

The previous prime is 1855791713. The next prime is 1855791737. The reversal of 1855791721 is 1271975581.

It is not a de Polignac number, because 1855791721 - 2³ = 1855791713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1855791761) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3129201 + ... + 3129793.

It is an arithmetic number, because the mean of its divisors is an integer number (70018344).

Almost surely, 2^1855791721 is an apocalyptic number.

It is an amenable number.

1855791721 is a deficient number, since it is larger than the sum of its proper divisors (384795287).

1855791721 is a wasteful number, since it uses less digits than its factorization.

1855791721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 961.

The product of its digits is 176400, while the sum is 46.

The square root of 1855791721 is about 43078.9011117972. The cubic root of 1855791721 is about 1228.8807587935.

It can be divided in two parts, 185 and 5791721, that added together give a triangular number (5791906 = T₃₄₀₃).

The spelling of 1855791721 in words is "one billion, eight hundred fifty-five million, seven hundred ninety-one thousand, seven hundred twenty-one".