123209981 has 2 divisors, whose sum is σ = 123209982. Its totient is φ = 123209980.

The previous prime is 123209971. The next prime is 123209987. The reversal of 123209981 is 189902321.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 108264025 + 14945956 = 10405^2 + 3866^2 .

It is a cyclic number.

It is not a de Polignac number, because 123209981 - 2⁶ = 123209917 is a prime.

It is a super-2 number, since 2×123209981² = 30361398836040722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (123209987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 61604990 + 61604991.

It is an arithmetic number, because the mean of its divisors is an integer number (61604991).

Almost surely, 2^123209981 is an apocalyptic number.

It is an amenable number.

123209981 is a deficient number, since it is larger than the sum of its proper divisors (1).

123209981 is an equidigital number, since it uses as much as digits as its factorization.

123209981 is an evil number, because the sum of its binary digits is even.

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

The square root of 123209981 is about 11099.9991441441. Note that the first 3 decimals coincide. The cubic root of 123209981 is about 497.6018238927.

The spelling of 123209981 in words is "one hundred twenty-three million, two hundred nine thousand, nine hundred eighty-one".