1917131981 has 2 divisors, whose sum is σ = 1917131982. Its totient is φ = 1917131980.

The previous prime is 1917131969. The next prime is 1917131999. The reversal of 1917131981 is 1891317191.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 975562756 + 941569225 = 31234^2 + 30685^2 .

It is a cyclic number.

It is not a de Polignac number, because 1917131981 - 2⁶ = 1917131917 is a prime.

It is a super-2 number, since 2×1917131981² = 7350790065145968722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1917131941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 958565990 + 958565991.

It is an arithmetic number, because the mean of its divisors is an integer number (958565991).

Almost surely, 2^1917131981 is an apocalyptic number.

It is an amenable number.

1917131981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1917131981 is an equidigital number, since it uses as much as digits as its factorization.

1917131981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 13608, while the sum is 41.

The square root of 1917131981 is about 43785.0657302236. The cubic root of 1917131981 is about 1242.2738327416.

The spelling of 1917131981 in words is "one billion, nine hundred seventeen million, one hundred thirty-one thousand, nine hundred eighty-one".