21007019977 has 2 divisors, whose sum is σ = 21007019978. Its totient is φ = 21007019976.

The previous prime is 21007019941. The next prime is 21007019983. The reversal of 21007019977 is 77991070012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18752289721 + 2254730256 = 136939^2 + 47484^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21007019977 is a prime.

It is not a weakly prime, because it can be changed into another prime (21007019987) 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, 10503509988 + 10503509989.

It is an arithmetic number, because the mean of its divisors is an integer number (10503509989).

Almost surely, 2^21007019977 is an apocalyptic number.

It is an amenable number.

21007019977 is a deficient number, since it is larger than the sum of its proper divisors (1).

21007019977 is an equidigital number, since it uses as much as digits as its factorization.

21007019977 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 55566, while the sum is 43.

Adding to 21007019977 its reverse (77991070012), we get a palindrome (98998089989).

The spelling of 21007019977 in words is "twenty-one billion, seven million, nineteen thousand, nine hundred seventy-seven".