642657909 has 8 divisors (see below), whose sum is σ = 868615552. Its totient is φ = 422569440.

The previous prime is 642657907. The next prime is 642657923. The reversal of 642657909 is 909756246.

642657909 = 2931² + 2932² + ... + 3003².

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 642657909 - 2¹ = 642657907 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 (642657901) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1467037 + ... + 1467474.

It is an arithmetic number, because the mean of its divisors is an integer number (108576944).

Almost surely, 2^642657909 is an apocalyptic number.

It is an amenable number.

642657909 is a deficient number, since it is larger than the sum of its proper divisors (225957643).

642657909 is a wasteful number, since it uses less digits than its factorization.

642657909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2934587.

The product of its (nonzero) digits is 816480, while the sum is 48.

The square root of 642657909 is about 25350.6983927465. The cubic root of 642657909 is about 862.9652057061.

The spelling of 642657909 in words is "six hundred forty-two million, six hundred fifty-seven thousand, nine hundred nine".