1861591 has 2 divisors, whose sum is σ = 1861592. Its totient is φ = 1861590.

The previous prime is 1861589. The next prime is 1861621. The reversal of 1861591 is 1951681.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1861591 - 2¹ = 1861589 is a prime.

Together with 1861589, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1861501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 930795 + 930796.

It is an arithmetic number, because the mean of its divisors is an integer number (930796).

2^1861591 is an apocalyptic number.

1861591 is a deficient number, since it is larger than the sum of its proper divisors (1).

1861591 is an equidigital number, since it uses as much as digits as its factorization.

1861591 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2160, while the sum is 31.

The square root of 1861591 is about 1364.4013339190. The cubic root of 1861591 is about 123.0159496359.

The spelling of 1861591 in words is "one million, eight hundred sixty-one thousand, five hundred ninety-one".