638972947 has 2 divisors, whose sum is σ = 638972948. Its totient is φ = 638972946.

The previous prime is 638972861. The next prime is 638972969. The reversal of 638972947 is 749279836.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 638972947 - 2¹⁵ = 638940179 is a prime.

It is not a weakly prime, because it can be changed into another prime (638972977) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319486473 + 319486474.

It is an arithmetic number, because the mean of its divisors is an integer number (319486474).

Almost surely, 2^638972947 is an apocalyptic number.

638972947 is a deficient number, since it is larger than the sum of its proper divisors (1).

638972947 is an equidigital number, since it uses as much as digits as its factorization.

638972947 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4572288, while the sum is 55.

The square root of 638972947 is about 25277.9142137954. The cubic root of 638972947 is about 861.3126461579.

The spelling of 638972947 in words is "six hundred thirty-eight million, nine hundred seventy-two thousand, nine hundred forty-seven".