135491981 has 2 divisors, whose sum is σ = 135491982. Its totient is φ = 135491980.

The previous prime is 135491977. The next prime is 135491999. The reversal of 135491981 is 189194531.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 123965956 + 11526025 = 11134^2 + 3395^2 .

It is an emirp because it is prime and its reverse (189194531) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 135491981 - 2² = 135491977 is a prime.

It is a super-2 number, since 2×135491981² = 36716153830608722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (135497981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 67745990 + 67745991.

It is an arithmetic number, because the mean of its divisors is an integer number (67745991).

Almost surely, 2^135491981 is an apocalyptic number.

It is an amenable number.

135491981 is a deficient number, since it is larger than the sum of its proper divisors (1).

135491981 is an equidigital number, since it uses as much as digits as its factorization.

135491981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 38880, while the sum is 41.

The square root of 135491981 is about 11640.1022761830. The cubic root of 135491981 is about 513.6151956960.

The spelling of 135491981 in words is "one hundred thirty-five million, four hundred ninety-one thousand, nine hundred eighty-one".