647720639 has 2 divisors, whose sum is σ = 647720640. Its totient is φ = 647720638.

The previous prime is 647720543. The next prime is 647720657. The reversal of 647720639 is 936027746.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-647720639 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 647720639.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (647720669) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323860319 + 323860320.

It is an arithmetic number, because the mean of its divisors is an integer number (323860320).

Almost surely, 2^647720639 is an apocalyptic number.

647720639 is a deficient number, since it is larger than the sum of its proper divisors (1).

647720639 is an equidigital number, since it uses as much as digits as its factorization.

647720639 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 381024, while the sum is 44.

The square root of 647720639 is about 25450.3563629274. The cubic root of 647720639 is about 865.2253699018.

The spelling of 647720639 in words is "six hundred forty-seven million, seven hundred twenty thousand, six hundred thirty-nine".