21021011993 has 2 divisors, whose sum is σ = 21021011994. Its totient is φ = 21021011992.

The previous prime is 21021011987. The next prime is 21021012029. The reversal of 21021011993 is 39911012012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16171700224 + 4849311769 = 127168^2 + 69637^2 .

It is a cyclic number.

It is not a de Polignac number, because 21021011993 - 2²⁰ = 21019963417 is a prime.

It is not a weakly prime, because it can be changed into another prime (21021011953) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510505996 + 10510505997.

It is an arithmetic number, because the mean of its divisors is an integer number (10510505997).

Almost surely, 2^21021011993 is an apocalyptic number.

It is an amenable number.

21021011993 is a deficient number, since it is larger than the sum of its proper divisors (1).

21021011993 is an equidigital number, since it uses as much as digits as its factorization.

21021011993 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 972, while the sum is 29.

The spelling of 21021011993 in words is "twenty-one billion, twenty-one million, eleven thousand, nine hundred ninety-three".