123391781 has 8 divisors (see below), whose sum is σ = 131097720. Its totient is φ = 115915968.

The previous prime is 123391777. The next prime is 123391787. The reversal of 123391781 is 187193321.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 28718881 + 94672900 = 5359^2 + 9730^2 .

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

It is not a de Polignac number, because 123391781 - 2² = 123391777 is a prime.

It is a super-2 number, since 2×123391781² = 30451063236703922, 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 (123391787) 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, 56426 + ... + 58571.

It is an arithmetic number, because the mean of its divisors is an integer number (16387215).

Almost surely, 2^123391781 is an apocalyptic number.

It is an amenable number.

123391781 is a deficient number, since it is larger than the sum of its proper divisors (7705939).

123391781 is a wasteful number, since it uses less digits than its factorization.

123391781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115063.

The product of its digits is 9072, while the sum is 35.

The square root of 123391781 is about 11108.1853153429. The cubic root of 123391781 is about 497.8464457250.

The spelling of 123391781 in words is "one hundred twenty-three million, three hundred ninety-one thousand, seven hundred eighty-one".