638968849 has 2 divisors, whose sum is σ = 638968850. Its totient is φ = 638968848.

The previous prime is 638968823. The next prime is 638968859. The reversal of 638968849 is 948869836.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 638471824 + 497025 = 25268^2 + 705^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-638968849 is a prime.

It is not a weakly prime, because it can be changed into another prime (638968859) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319484424 + 319484425.

It is an arithmetic number, because the mean of its divisors is an integer number (319484425).

Almost surely, 2^638968849 is an apocalyptic number.

It is an amenable number.

638968849 is a deficient number, since it is larger than the sum of its proper divisors (1).

638968849 is an equidigital number, since it uses as much as digits as its factorization.

638968849 is an evil number, because the sum of its binary digits is even.

The product of its digits is 17915904, while the sum is 61.

The square root of 638968849 is about 25277.8331547623. The cubic root of 638968849 is about 861.3108048349.

The spelling of 638968849 in words is "six hundred thirty-eight million, nine hundred sixty-eight thousand, eight hundred forty-nine".