21020873197 has 4 divisors (see below), whose sum is σ = 21417493500. Its totient is φ = 20624252896.

The previous prime is 21020873189. The next prime is 21020873221. The reversal of 21020873197 is 79137802012.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10639097316 + 10381775881 = 103146^2 + 101891^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020873197 - 2³ = 21020873189 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020873177) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 198310072 + ... + 198310177.

It is an arithmetic number, because the mean of its divisors is an integer number (5354373375).

Almost surely, 2^21020873197 is an apocalyptic number.

It is an amenable number.

21020873197 is a deficient number, since it is larger than the sum of its proper divisors (396620303).

21020873197 is an equidigital number, since it uses as much as digits as its factorization.

21020873197 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 396620302.

The product of its (nonzero) digits is 42336, while the sum is 40.

The spelling of 21020873197 in words is "twenty-one billion, twenty million, eight hundred seventy-three thousand, one hundred ninety-seven".