649878989 has 4 divisors (see below), whose sum is σ = 667443324. Its totient is φ = 632314656.

The previous prime is 649878967. The next prime is 649879003. The reversal of 649878989 is 989878946.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 508863364 + 141015625 = 22558^2 + 11875^2 .

It is a cyclic number.

It is not a de Polignac number, because 649878989 - 2²⁸ = 381443533 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 (649878919) 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, 8782112 + ... + 8782185.

It is an arithmetic number, because the mean of its divisors is an integer number (166860831).

Almost surely, 2^649878989 is an apocalyptic number.

It is an amenable number.

649878989 is a deficient number, since it is larger than the sum of its proper divisors (17564335).

649878989 is a wasteful number, since it uses less digits than its factorization.

649878989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17564334.

The product of its digits is 62705664, while the sum is 68.

The square root of 649878989 is about 25492.7242365346. The cubic root of 649878989 is about 866.1853458711.

The spelling of 649878989 in words is "six hundred forty-nine million, eight hundred seventy-eight thousand, nine hundred eighty-nine".