1851621791 has 2 divisors, whose sum is σ = 1851621792. Its totient is φ = 1851621790.

The previous prime is 1851621767. The next prime is 1851621799. The reversal of 1851621791 is 1971261581.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1851621791 - 2¹⁸ = 1851359647 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1851621799) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 925810895 + 925810896.

It is an arithmetic number, because the mean of its divisors is an integer number (925810896).

Almost surely, 2^1851621791 is an apocalyptic number.

1851621791 is a deficient number, since it is larger than the sum of its proper divisors (1).

1851621791 is an equidigital number, since it uses as much as digits as its factorization.

1851621791 is an evil number, because the sum of its binary digits is even.

The product of its digits is 30240, while the sum is 41.

The square root of 1851621791 is about 43030.4751426242. The cubic root of 1851621791 is about 1227.9596443553.

The spelling of 1851621791 in words is "one billion, eight hundred fifty-one million, six hundred twenty-one thousand, seven hundred ninety-one".