21598428109 has 4 divisors (see below), whose sum is σ = 21656333116. Its totient is φ = 21540523104.

The previous prime is 21598428043. The next prime is 21598428143. The reversal of 21598428109 is 90182489512.

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 6128541225 + 15469886884 = 78285^2 + 124378^2 .

It is a cyclic number.

It is not a de Polignac number, because 21598428109 - 2¹¹ = 21598426061 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 (21598428169) 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, 28951944 + ... + 28952689.

It is an arithmetic number, because the mean of its divisors is an integer number (5414083279).

Almost surely, 2^21598428109 is an apocalyptic number.

It is an amenable number.

21598428109 is a deficient number, since it is larger than the sum of its proper divisors (57905007).

21598428109 is an equidigital number, since it uses as much as digits as its factorization.

21598428109 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57905006.

The product of its (nonzero) digits is 414720, while the sum is 49.

The spelling of 21598428109 in words is "twenty-one billion, five hundred ninety-eight million, four hundred twenty-eight thousand, one hundred nine".