21021020099 has 2 divisors, whose sum is σ = 21021020100. Its totient is φ = 21021020098.

The previous prime is 21021020089. The next prime is 21021020117. The reversal of 21021020099 is 99002012012.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21021020099 - 2²⁰ = 21019971523 is a prime.

It is not a weakly prime, because it can be changed into another prime (21021020089) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510510049 + 10510510050.

It is an arithmetic number, because the mean of its divisors is an integer number (10510510050).

Almost surely, 2^21021020099 is an apocalyptic number.

21021020099 is a deficient number, since it is larger than the sum of its proper divisors (1).

21021020099 is an equidigital number, since it uses as much as digits as its factorization.

21021020099 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 648, while the sum is 26.

It can be divided in two parts, 2102 and 1020099, that added together give a palindrome (1022201).

The spelling of 21021020099 in words is "twenty-one billion, twenty-one million, twenty thousand, ninety-nine".