2391721 has 2 divisors, whose sum is σ = 2391722. Its totient is φ = 2391720.

The previous prime is 2391709. The next prime is 2391733. The reversal of 2391721 is 1271932.

It is a balanced prime because it is at equal distance from previous prime (2391709) and next prime (2391733).

It can be written as a sum of positive squares in only one way, i.e., 1929321 + 462400 = 1389^2 + 680^2 .

It is a cyclic number.

It is not a de Polignac number, because 2391721 - 2¹⁵ = 2358953 is a prime.

It is not a weakly prime, because it can be changed into another prime (2391751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1195860 + 1195861.

It is an arithmetic number, because the mean of its divisors is an integer number (1195861).

2^2391721 is an apocalyptic number.

It is an amenable number.

2391721 is a deficient number, since it is larger than the sum of its proper divisors (1).

2391721 is an equidigital number, since it uses as much as digits as its factorization.

2391721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 756, while the sum is 25.

The square root of 2391721 is about 1546.5189943871. The cubic root of 2391721 is about 133.7324616710.

The spelling of 2391721 in words is "two million, three hundred ninety-one thousand, seven hundred twenty-one".