1656643409 has 2 divisors, whose sum is σ = 1656643410. Its totient is φ = 1656643408.

The previous prime is 1656643363. The next prime is 1656643411. The reversal of 1656643409 is 9043466561.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1614432400 + 42211009 = 40180^2 + 6497^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1656643409 is a prime.

Together with 1656643411, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1656643409.

It is not a weakly prime, because it can be changed into another prime (1656603409) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 828321704 + 828321705.

It is an arithmetic number, because the mean of its divisors is an integer number (828321705).

Almost surely, 2^1656643409 is an apocalyptic number.

It is an amenable number.

1656643409 is a deficient number, since it is larger than the sum of its proper divisors (1).

1656643409 is an equidigital number, since it uses as much as digits as its factorization.

1656643409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 466560, while the sum is 44.

The square root of 1656643409 is about 40701.8845878173. The cubic root of 1656643409 is about 1183.2495436980.

The spelling of 1656643409 in words is "one billion, six hundred fifty-six million, six hundred forty-three thousand, four hundred nine".