123400021 has 2 divisors, whose sum is σ = 123400022. Its totient is φ = 123400020.

The previous prime is 123399989. The next prime is 123400027. The reversal of 123400021 is 120004321.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 102111025 + 21288996 = 10105^2 + 4614^2 .

It is an emirp because it is prime and its reverse (120004321) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 123400021 - 2⁵ = 123399989 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 123399974 and 123400010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (123400027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 61700010 + 61700011.

It is an arithmetic number, because the mean of its divisors is an integer number (61700011).

Almost surely, 2^123400021 is an apocalyptic number.

It is an amenable number.

123400021 is a deficient number, since it is larger than the sum of its proper divisors (1).

123400021 is an equidigital number, since it uses as much as digits as its factorization.

123400021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 123400021 is about 11108.5562068164. The cubic root of 123400021 is about 497.8575274015.

Adding to 123400021 its reverse (120004321), we get a palindrome (243404342).

The spelling of 123400021 in words is "one hundred twenty-three million, four hundred thousand, twenty-one".