135816921 has 24 divisors (see below), whose sum is σ = 213175040. Its totient is φ = 83008800.

The previous prime is 135816917. The next prime is 135816929. The reversal of 135816921 is 129618531.

135816921 is a `hidden beast` number, since 13 + 581 + 69 + 2 + 1 = 666.

It is not a de Polignac number, because 135816921 - 2² = 135816917 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (135816929) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7510 + ... + 18111.

Almost surely, 2^135816921 is an apocalyptic number.

It is an amenable number.

135816921 is a deficient number, since it is larger than the sum of its proper divisors (77358119).

135816921 is a wasteful number, since it uses less digits than its factorization.

135816921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25677 (or 25674 counting only the distinct ones).

The product of its digits is 12960, while the sum is 36.

The square root of 135816921 is about 11654.0516988728. The cubic root of 135816921 is about 514.0254558494.

It can be divided in two parts, 13581 and 6921, that added together give a palindrome (20502).

The spelling of 135816921 in words is "one hundred thirty-five million, eight hundred sixteen thousand, nine hundred twenty-one".