21730505909 has 4 divisors (see below), whose sum is σ = 24834863904. Its totient is φ = 18626147916.

The previous prime is 21730505893. The next prime is 21730505959. The reversal of 21730505909 is 90950503712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21730505909 - 2⁴ = 21730505893 is a prime.

It is a super-2 number, since 2×21730505909² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21730505959) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1552178987 + ... + 1552179000.

It is an arithmetic number, because the mean of its divisors is an integer number (6208715976).

Almost surely, 2^21730505909 is an apocalyptic number.

It is an amenable number.

21730505909 is a deficient number, since it is larger than the sum of its proper divisors (3104357995).

21730505909 is an equidigital number, since it uses as much as digits as its factorization.

21730505909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3104357994.

The product of its (nonzero) digits is 85050, while the sum is 41.

The spelling of 21730505909 in words is "twenty-one billion, seven hundred thirty million, five hundred five thousand, nine hundred nine".