2661991 has 2 divisors, whose sum is σ = 2661992. Its totient is φ = 2661990.

The previous prime is 2661961. The next prime is 2662027. The reversal of 2661991 is 1991662.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 2661991 - 2⁵ = 2661959 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2661931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1330995 + 1330996.

It is an arithmetic number, because the mean of its divisors is an integer number (1330996).

2^2661991 is an apocalyptic number.

2661991 is a deficient number, since it is larger than the sum of its proper divisors (1).

2661991 is an equidigital number, since it uses as much as digits as its factorization.

2661991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5832, while the sum is 34.

The square root of 2661991 is about 1631.5609090684. The cubic root of 2661991 is about 138.5911592997.

The spelling of 2661991 in words is "two million, six hundred sixty-one thousand, nine hundred ninety-one".