2781991 has 2 divisors, whose sum is σ = 2781992. Its totient is φ = 2781990.

The previous prime is 2781983. The next prime is 2782001. The reversal of 2781991 is 1991872.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 2781991 - 2³ = 2781983 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 2781991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2781901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1390995 + 1390996.

It is an arithmetic number, because the mean of its divisors is an integer number (1390996).

2^2781991 is an apocalyptic number.

2781991 is a deficient number, since it is larger than the sum of its proper divisors (1).

2781991 is an equidigital number, since it uses as much as digits as its factorization.

2781991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072, while the sum is 37.

The square root of 2781991 is about 1667.9301544129. The cubic root of 2781991 is about 140.6431463661.

The spelling of 2781991 in words is "two million, seven hundred eighty-one thousand, nine hundred ninety-one".