21123021977 has 2 divisors, whose sum is σ = 21123021978. Its totient is φ = 21123021976.

The previous prime is 21123021971. The next prime is 21123022007. The reversal of 21123021977 is 77912032112.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18051534736 + 3071487241 = 134356^2 + 55421^2 .

It is a cyclic number.

It is not a de Polignac number, because 21123021977 - 2⁸ = 21123021721 is a prime.

It is not a weakly prime, because it can be changed into another prime (21123021971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561510988 + 10561510989.

It is an arithmetic number, because the mean of its divisors is an integer number (10561510989).

Almost surely, 2^21123021977 is an apocalyptic number.

It is an amenable number.

21123021977 is a deficient number, since it is larger than the sum of its proper divisors (1).

21123021977 is an equidigital number, since it uses as much as digits as its factorization.

21123021977 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10584, while the sum is 35.

The spelling of 21123021977 in words is "twenty-one billion, one hundred twenty-three million, twenty-one thousand, nine hundred seventy-seven".