21509339090 has 16 divisors (see below), whose sum is σ = 38728295640. Its totient is φ = 8601183360.

The previous prime is 21509339087. The next prime is 21509339099. The reversal of 21509339090 is 9093390512.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 20604592849 + 904746241 = 143543^2 + 30079^2 .

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21509339099) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 283451 + ... + 351230.

Almost surely, 2^21509339090 is an apocalyptic number.

21509339090 is a deficient number, since it is larger than the sum of its proper divisors (17218956550).

21509339090 is a wasteful number, since it uses less digits than its factorization.

21509339090 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 638077.

The product of its (nonzero) digits is 65610, while the sum is 41.

The spelling of 21509339090 in words is "twenty-one billion, five hundred nine million, three hundred thirty-nine thousand, ninety".