1645856789 has 2 divisors, whose sum is σ = 1645856790. Its totient is φ = 1645856788.

The previous prime is 1645856689. The next prime is 1645856801. The reversal of 1645856789 is 9876585461.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1620706564 + 25150225 = 40258^2 + 5015^2 .

It is a cyclic number.

It is not a de Polignac number, because 1645856789 - 2¹² = 1645852693 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1645856489) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 822928394 + 822928395.

It is an arithmetic number, because the mean of its divisors is an integer number (822928395).

Almost surely, 2^1645856789 is an apocalyptic number.

It is an amenable number.

1645856789 is a deficient number, since it is larger than the sum of its proper divisors (1).

1645856789 is an equidigital number, since it uses as much as digits as its factorization.

1645856789 is an evil number, because the sum of its binary digits is even.

The product of its digits is 14515200, while the sum is 59.

The square root of 1645856789 is about 40569.1605656316. The cubic root of 1645856789 is about 1180.6758526528.

The spelling of 1645856789 in words is "one billion, six hundred forty-five million, eight hundred fifty-six thousand, seven hundred eighty-nine".