2145721 has 2 divisors, whose sum is σ = 2145722. Its totient is φ = 2145720.

The previous prime is 2145713. The next prime is 2145763. The reversal of 2145721 is 1275412.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1123600 + 1022121 = 1060^2 + 1011^2 .

It is a cyclic number.

It is not a de Polignac number, because 2145721 - 2³ = 2145713 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 2145692 and 2145701.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2145421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1072860 + 1072861.

It is an arithmetic number, because the mean of its divisors is an integer number (1072861).

2^2145721 is an apocalyptic number.

It is an amenable number.

2145721 is a deficient number, since it is larger than the sum of its proper divisors (1).

2145721 is an equidigital number, since it uses as much as digits as its factorization.

2145721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 560, while the sum is 22.

The square root of 2145721 is about 1464.8279762484. The cubic root of 2145721 is about 128.9806072244.

The spelling of 2145721 in words is "two million, one hundred forty-five thousand, seven hundred twenty-one".