21021019997 has 2 divisors, whose sum is σ = 21021019998. Its totient is φ = 21021019996.

The previous prime is 21021019967. The next prime is 21021020057. The reversal of 21021019997 is 79991012012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14403360196 + 6617659801 = 120014^2 + 81349^2 .

It is a cyclic number.

It is not a de Polignac number, because 21021019997 - 2¹⁰ = 21021018973 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21021019937) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510509998 + 10510509999.

It is an arithmetic number, because the mean of its divisors is an integer number (10510509999).

Almost surely, 2^21021019997 is an apocalyptic number.

It is an amenable number.

21021019997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21021019997 is an equidigital number, since it uses as much as digits as its factorization.

21021019997 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20412, while the sum is 41.

The spelling of 21021019997 in words is "twenty-one billion, twenty-one million, nineteen thousand, nine hundred ninety-seven".