646669549 has 4 divisors (see below), whose sum is σ = 646724736. Its totient is φ = 646614364.

The previous prime is 646669523. The next prime is 646669571. The reversal of 646669549 is 945966646.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 646669549 - 2¹⁹ = 646145261 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 646669549.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646669249) 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, 2269 + ... + 36034.

It is an arithmetic number, because the mean of its divisors is an integer number (161681184).

It is a 11718-hyperperfect number.

Almost surely, 2^646669549 is an apocalyptic number.

It is an amenable number.

646669549 is a deficient number, since it is larger than the sum of its proper divisors (55187).

646669549 is a wasteful number, since it uses less digits than its factorization.

646669549 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55186.

The product of its digits is 8398080, while the sum is 55.

The square root of 646669549 is about 25429.6981696598. The cubic root of 646669549 is about 864.7571010991.

The spelling of 646669549 in words is "six hundred forty-six million, six hundred sixty-nine thousand, five hundred forty-nine".