135991661 has 8 divisors (see below), whose sum is σ = 147198744. Its totient is φ = 124891200.

The previous prime is 135991651. The next prime is 135991679. The reversal of 135991661 is 166199531.

It can be written as a sum of positive squares in 4 ways, for example, as 58446025 + 77545636 = 7645^2 + 8806^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-135991661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (135991601) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 23990 + ... + 29111.

It is an arithmetic number, because the mean of its divisors is an integer number (18399843).

Almost surely, 2^135991661 is an apocalyptic number.

It is an amenable number.

135991661 is a deficient number, since it is larger than the sum of its proper divisors (11207083).

135991661 is a wasteful number, since it uses less digits than its factorization.

135991661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53311.

The product of its digits is 43740, while the sum is 41.

The square root of 135991661 is about 11661.5462525344. The cubic root of 135991661 is about 514.2458071731.

The spelling of 135991661 in words is "one hundred thirty-five million, nine hundred ninety-one thousand, six hundred sixty-one".