1971931639 has 2 divisors, whose sum is σ = 1971931640. Its totient is φ = 1971931638.

The previous prime is 1971931579. The next prime is 1971931651. The reversal of 1971931639 is 9361391791.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1971931639 - 2⁹ = 1971931127 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1971931592 and 1971931601.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1971935639) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 985965819 + 985965820.

It is an arithmetic number, because the mean of its divisors is an integer number (985965820).

Almost surely, 2^1971931639 is an apocalyptic number.

1971931639 is a deficient number, since it is larger than the sum of its proper divisors (1).

1971931639 is an equidigital number, since it uses as much as digits as its factorization.

1971931639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 275562, while the sum is 49.

The square root of 1971931639 is about 44406.4369095292. The cubic root of 1971931639 is about 1253.9992739868. Note that the first 3 decimals are identical.

The spelling of 1971931639 in words is "one billion, nine hundred seventy-one million, nine hundred thirty-one thousand, six hundred thirty-nine".