645771439 has 4 divisors (see below), whose sum is σ = 648069840. Its totient is φ = 643473040.

The previous prime is 645771433. The next prime is 645771499. The reversal of 645771439 is 934177546.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 645771439 - 2³ = 645771431 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645771431) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1148779 + ... + 1149340.

It is an arithmetic number, because the mean of its divisors is an integer number (162017460).

Almost surely, 2^645771439 is an apocalyptic number.

645771439 is a deficient number, since it is larger than the sum of its proper divisors (2298401).

645771439 is a wasteful number, since it uses less digits than its factorization.

645771439 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2298400.

The product of its digits is 635040, while the sum is 46.

The square root of 645771439 is about 25412.0333503638. The cubic root of 645771439 is about 864.3565839051.

It can be divided in two parts, 64 and 5771439, that added together give a triangular number (5771503 = T₃₃₉₇).

The spelling of 645771439 in words is "six hundred forty-five million, seven hundred seventy-one thousand, four hundred thirty-nine".