639934381 has 2 divisors, whose sum is σ = 639934382. Its totient is φ = 639934380.

The previous prime is 639934357. The next prime is 639934423. The reversal of 639934381 is 183439936.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 579172356 + 60762025 = 24066^2 + 7795^2 .

It is a cyclic number.

It is not a de Polignac number, because 639934381 - 2¹⁷ = 639803309 is a prime.

It is a super-2 number, since 2×639934381² = 819032023971706322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (639934181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319967190 + 319967191.

It is an arithmetic number, because the mean of its divisors is an integer number (319967191).

Almost surely, 2^639934381 is an apocalyptic number.

It is an amenable number.

639934381 is a deficient number, since it is larger than the sum of its proper divisors (1).

639934381 is an equidigital number, since it uses as much as digits as its factorization.

639934381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 419904, while the sum is 46.

The square root of 639934381 is about 25296.9243387413. The cubic root of 639934381 is about 861.7444225374.

The spelling of 639934381 in words is "six hundred thirty-nine million, nine hundred thirty-four thousand, three hundred eighty-one".