21609985393 has 4 divisors (see below), whose sum is σ = 22307081728. Its totient is φ = 20912889060.

The previous prime is 21609985373. The next prime is 21609985429. The reversal of 21609985393 is 39358990612.

It is a happy number.

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 21609985393 - 2²⁹ = 21073114481 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21609985343) 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, 348548121 + ... + 348548182.

It is an arithmetic number, because the mean of its divisors is an integer number (5576770432).

Almost surely, 2^21609985393 is an apocalyptic number.

It is an amenable number.

21609985393 is a deficient number, since it is larger than the sum of its proper divisors (697096335).

21609985393 is an equidigital number, since it uses as much as digits as its factorization.

21609985393 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 697096334.

The product of its (nonzero) digits is 3149280, while the sum is 55.

The spelling of 21609985393 in words is "twenty-one billion, six hundred nine million, nine hundred eighty-five thousand, three hundred ninety-three".