21720735609 has 16 divisors (see below), whose sum is σ = 30490771200. Its totient is φ = 13715871696.

The previous prime is 21720735583. The next prime is 21720735611. The reversal of 21720735609 is 90653702712.

It is not a de Polignac number, because 21720735609 - 2¹⁷ = 21720604537 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21720735409) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 312922 + ... + 375980.

It is an arithmetic number, because the mean of its divisors is an integer number (1905673200).

Almost surely, 2^21720735609 is an apocalyptic number.

It is an amenable number.

21720735609 is a deficient number, since it is larger than the sum of its proper divisors (8770035591).

21720735609 is a wasteful number, since it uses less digits than its factorization.

21720735609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69124.

The product of its (nonzero) digits is 158760, while the sum is 42.

The spelling of 21720735609 in words is "twenty-one billion, seven hundred twenty million, seven hundred thirty-five thousand, six hundred nine".