135680021 has 2 divisors, whose sum is σ = 135680022. Its totient is φ = 135680020.

The previous prime is 135680003. The next prime is 135680047. The reversal of 135680021 is 120086531.

It is an a-pointer prime, because the next prime (135680047) can be obtained adding 135680021 to its sum of digits (26).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 122899396 + 12780625 = 11086^2 + 3575^2 .

It is an emirp because it is prime and its reverse (120086531) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 135680021 - 2¹⁰ = 135678997 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (135680071) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 67840010 + 67840011.

It is an arithmetic number, because the mean of its divisors is an integer number (67840011).

Almost surely, 2^135680021 is an apocalyptic number.

It is an amenable number.

135680021 is a deficient number, since it is larger than the sum of its proper divisors (1).

135680021 is an equidigital number, since it uses as much as digits as its factorization.

135680021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 135680021 is about 11648.1767242775. The cubic root of 135680021 is about 513.8526895957.

The spelling of 135680021 in words is "one hundred thirty-five million, six hundred eighty thousand, twenty-one".