21065021977 has 2 divisors, whose sum is σ = 21065021978. Its totient is φ = 21065021976.

The previous prime is 21065021959. The next prime is 21065021981. The reversal of 21065021977 is 77912056012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15863150601 + 5201871376 = 125949^2 + 72124^2 .

It is a cyclic number.

It is not a de Polignac number, because 21065021977 - 2⁷ = 21065021849 is a prime.

It is not a weakly prime, because it can be changed into another prime (21065021917) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10532510988 + 10532510989.

It is an arithmetic number, because the mean of its divisors is an integer number (10532510989).

Almost surely, 2^21065021977 is an apocalyptic number.

It is an amenable number.

21065021977 is a deficient number, since it is larger than the sum of its proper divisors (1).

21065021977 is an equidigital number, since it uses as much as digits as its factorization.

21065021977 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 52920, while the sum is 40.

Adding to 21065021977 its reverse (77912056012), we get a palindrome (98977077989).

The spelling of 21065021977 in words is "twenty-one billion, sixty-five million, twenty-one thousand, nine hundred seventy-seven".