642747221 has 4 divisors (see below), whose sum is σ = 643220844. Its totient is φ = 642273600.

The previous prime is 642747197. The next prime is 642747223. The reversal of 642747221 is 122747246.

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 40780996 + 601966225 = 6386^2 + 24535^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-642747221 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 (642747223) 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, 234770 + ... + 237491.

It is an arithmetic number, because the mean of its divisors is an integer number (160805211).

Almost surely, 2^642747221 is an apocalyptic number.

It is an amenable number.

642747221 is a deficient number, since it is larger than the sum of its proper divisors (473623).

642747221 is a wasteful number, since it uses less digits than its factorization.

642747221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 473622.

The product of its digits is 37632, while the sum is 35.

The square root of 642747221 is about 25352.4598609287. The cubic root of 642747221 is about 863.0051800986.

The spelling of 642747221 in words is "six hundred forty-two million, seven hundred forty-seven thousand, two hundred twenty-one".