1971981617 has 2 divisors, whose sum is σ = 1971981618. Its totient is φ = 1971981616.

The previous prime is 1971981581. The next prime is 1971981629. The reversal of 1971981617 is 7161891791.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1904100496 + 67881121 = 43636^2 + 8239^2 .

It is a cyclic number.

It is not a de Polignac number, because 1971981617 - 2¹² = 1971977521 is a prime.

It is a super-2 number, since 2×1971981617² = 7777422995571869378, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1971981667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 985990808 + 985990809.

It is an arithmetic number, because the mean of its divisors is an integer number (985990809).

Almost surely, 2^1971981617 is an apocalyptic number.

It is an amenable number.

1971981617 is a deficient number, since it is larger than the sum of its proper divisors (1).

1971981617 is an equidigital number, since it uses as much as digits as its factorization.

1971981617 is an evil number, because the sum of its binary digits is even.

The product of its digits is 190512, while the sum is 50.

The square root of 1971981617 is about 44406.9996396964. Note that the first 3 decimals coincide. The cubic root of 1971981617 is about 1254.0098679724.

The spelling of 1971981617 in words is "one billion, nine hundred seventy-one million, nine hundred eighty-one thousand, six hundred seventeen".