123775721 has 2 divisors, whose sum is σ = 123775722. Its totient is φ = 123775720.

The previous prime is 123775697. The next prime is 123775837. The reversal of 123775721 is 127577321.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 102799321 + 20976400 = 10139^2 + 4580^2 .

It is an emirp because it is prime and its reverse (127577321) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-123775721 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (123775021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 61887860 + 61887861.

It is an arithmetic number, because the mean of its divisors is an integer number (61887861).

Almost surely, 2^123775721 is an apocalyptic number.

It is an amenable number.

123775721 is a deficient number, since it is larger than the sum of its proper divisors (1).

123775721 is an equidigital number, since it uses as much as digits as its factorization.

123775721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20580, while the sum is 35.

The square root of 123775721 is about 11125.4537435558. The cubic root of 123775721 is about 498.3622695347.

The spelling of 123775721 in words is "one hundred twenty-three million, seven hundred seventy-five thousand, seven hundred twenty-one".