135243821 has 4 divisors (see below), whose sum is σ = 136484700. Its totient is φ = 134002944.

The previous prime is 135243817. The next prime is 135243833. The reversal of 135243821 is 128342531.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 128342531 = 79 ⋅1624589.

It can be written as a sum of positive squares in 2 ways, for example, as 119355625 + 15888196 = 10925^2 + 3986^2 .

It is a cyclic number.

It is not a de Polignac number, because 135243821 - 2² = 135243817 is a prime.

It is a super-2 number, since 2×135243821² = 36581782237360082, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (135213821) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 620276 + ... + 620493.

It is an arithmetic number, because the mean of its divisors is an integer number (34121175).

Almost surely, 2^135243821 is an apocalyptic number.

It is an amenable number.

135243821 is a deficient number, since it is larger than the sum of its proper divisors (1240879).

135243821 is a wasteful number, since it uses less digits than its factorization.

135243821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1240878.

The product of its digits is 5760, while the sum is 29.

The square root of 135243821 is about 11629.4376906194. The cubic root of 135243821 is about 513.3014338510.

The spelling of 135243821 in words is "one hundred thirty-five million, two hundred forty-three thousand, eight hundred twenty-one".