21123031877 has 2 divisors, whose sum is σ = 21123031878. Its totient is φ = 21123031876.

The previous prime is 21123031849. The next prime is 21123031883. The reversal of 21123031877 is 77813032112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17494294756 + 3628737121 = 132266^2 + 60239^2 .

It is a cyclic number.

It is not a de Polignac number, because 21123031877 - 2³⁴ = 3943162693 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21123031477) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561515938 + 10561515939.

It is an arithmetic number, because the mean of its divisors is an integer number (10561515939).

Almost surely, 2^21123031877 is an apocalyptic number.

It is an amenable number.

21123031877 is a deficient number, since it is larger than the sum of its proper divisors (1).

21123031877 is an equidigital number, since it uses as much as digits as its factorization.

21123031877 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 14112, while the sum is 35.

Adding to 21123031877 its reverse (77813032112), we get a palindrome (98936063989).

The spelling of 21123031877 in words is "twenty-one billion, one hundred twenty-three million, thirty-one thousand, eight hundred seventy-seven".