123136421 has 4 divisors (see below), whose sum is σ = 123158700. Its totient is φ = 123114144.

The previous prime is 123136399. The next prime is 123136451. The reversal of 123136421 is 124631321.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 124631321 = 389 ⋅320389.

It can be written as a sum of positive squares in 2 ways, for example, as 120143521 + 2992900 = 10961^2 + 1730^2 .

It is a cyclic number.

It is not a de Polignac number, because 123136421 - 2⁶ = 123136357 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (123136451) 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, 4115 + ... + 16223.

It is an arithmetic number, because the mean of its divisors is an integer number (30789675).

Almost surely, 2^123136421 is an apocalyptic number.

It is an amenable number.

123136421 is a deficient number, since it is larger than the sum of its proper divisors (22279).

123136421 is a wasteful number, since it uses less digits than its factorization.

123136421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22278.

The product of its digits is 864, while the sum is 23.

The square root of 123136421 is about 11096.6851356610. The cubic root of 123136421 is about 497.5027765137.

Adding to 123136421 its reverse (124631321), we get a palindrome (247767742).

The spelling of 123136421 in words is "one hundred twenty-three million, one hundred thirty-six thousand, four hundred twenty-one".