2640721 has 2 divisors, whose sum is σ = 2640722. Its totient is φ = 2640720.

The previous prime is 2640713. The next prime is 2640739. The reversal of 2640721 is 1270462.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1527696 + 1113025 = 1236^2 + 1055^2 .

It is a cyclic number.

It is not a de Polignac number, because 2640721 - 2³ = 2640713 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 2640692 and 2640701.

It is not a weakly prime, because it can be changed into another prime (2640761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1320360 + 1320361.

It is an arithmetic number, because the mean of its divisors is an integer number (1320361).

2^2640721 is an apocalyptic number.

It is an amenable number.

2640721 is a deficient number, since it is larger than the sum of its proper divisors (1).

2640721 is an equidigital number, since it uses as much as digits as its factorization.

2640721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 672, while the sum is 22.

The square root of 2640721 is about 1625.0295381931. The cubic root of 2640721 is about 138.2210453114.

The spelling of 2640721 in words is "two million, six hundred forty thousand, seven hundred twenty-one".