1861722991 has 2 divisors, whose sum is σ = 1861722992. Its totient is φ = 1861722990.

The previous prime is 1861722983. The next prime is 1861723013. The reversal of 1861722991 is 1992271681.

It is a weak prime.

It is an emirp because it is prime and its reverse (1992271681) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1861722991 - 2³ = 1861722983 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1861722901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 930861495 + 930861496.

It is an arithmetic number, because the mean of its divisors is an integer number (930861496).

Almost surely, 2^1861722991 is an apocalyptic number.

1861722991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1861722991 is an equidigital number, since it uses as much as digits as its factorization.

1861722991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 108864, while the sum is 46.

The square root of 1861722991 is about 43147.6881304202. The cubic root of 1861722991 is about 1230.1885693663.

The spelling of 1861722991 in words is "one billion, eight hundred sixty-one million, seven hundred twenty-two thousand, nine hundred ninety-one".