123821909 has 4 divisors (see below), whose sum is σ = 128091660. Its totient is φ = 119552160.

The previous prime is 123821891. The next prime is 123821911. The reversal of 123821909 is 909128321.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 77880625 + 45941284 = 8825^2 + 6778^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-123821909 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 (123821959) 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, 2134832 + ... + 2134889.

It is an arithmetic number, because the mean of its divisors is an integer number (32022915).

Almost surely, 2^123821909 is an apocalyptic number.

It is an amenable number.

123821909 is a deficient number, since it is larger than the sum of its proper divisors (4269751).

123821909 is an equidigital number, since it uses as much as digits as its factorization.

123821909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4269750.

The product of its (nonzero) digits is 7776, while the sum is 35.

The square root of 123821909 is about 11127.5293304489. The cubic root of 123821909 is about 498.4242512485.

The spelling of 123821909 in words is "one hundred twenty-three million, eight hundred twenty-one thousand, nine hundred nine".