123135781 has 2 divisors, whose sum is σ = 123135782. Its totient is φ = 123135780.

The previous prime is 123135757. The next prime is 123135821. The reversal of 123135781 is 187531321.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 121903681 + 1232100 = 11041^2 + 1110^2 .

It is a cyclic number.

It is not a de Polignac number, because 123135781 - 2¹¹ = 123133733 is a prime.

It is a super-2 number, since 2×123135781² = 30324841124959922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (123105781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 61567890 + 61567891.

It is an arithmetic number, because the mean of its divisors is an integer number (61567891).

Almost surely, 2^123135781 is an apocalyptic number.

It is an amenable number.

123135781 is a deficient number, since it is larger than the sum of its proper divisors (1).

123135781 is an equidigital number, since it uses as much as digits as its factorization.

123135781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5040, while the sum is 31.

The square root of 123135781 is about 11096.6562981828. The cubic root of 123135781 is about 497.5019145907.

The spelling of 123135781 in words is "one hundred twenty-three million, one hundred thirty-five thousand, seven hundred eighty-one".