1653721 has 2 divisors, whose sum is σ = 1653722. Its totient is φ = 1653720.

The previous prime is 1653697. The next prime is 1653731. The reversal of 1653721 is 1273561.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1527696 + 126025 = 1236^2 + 355^2 .

It is an emirp because it is prime and its reverse (1273561) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1653721 - 2⁵ = 1653689 is a prime.

It is not a weakly prime, because it can be changed into another prime (1653731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 826860 + 826861.

It is an arithmetic number, because the mean of its divisors is an integer number (826861).

2^1653721 is an apocalyptic number.

It is an amenable number.

1653721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1653721 is an equidigital number, since it uses as much as digits as its factorization.

1653721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1260, while the sum is 25.

The square root of 1653721 is about 1285.9708394828. The cubic root of 1653721 is about 118.2553362005.

The spelling of 1653721 in words is "one million, six hundred fifty-three thousand, seven hundred twenty-one".