21535609917 has 4 divisors (see below), whose sum is σ = 28714146560. Its totient is φ = 14357073276.

The previous prime is 21535609889. The next prime is 21535609957. The reversal of 21535609917 is 71990653512.

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 not a de Polignac number, because 21535609917 - 2¹⁴ = 21535593533 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 (21535609957) 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, 3589268317 + ... + 3589268322.

It is an arithmetic number, because the mean of its divisors is an integer number (7178536640).

Almost surely, 2^21535609917 is an apocalyptic number.

It is an amenable number.

21535609917 is a deficient number, since it is larger than the sum of its proper divisors (7178536643).

21535609917 is an equidigital number, since it uses as much as digits as its factorization.

21535609917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7178536642.

The product of its (nonzero) digits is 510300, while the sum is 48.

The spelling of 21535609917 in words is "twenty-one billion, five hundred thirty-five million, six hundred nine thousand, nine hundred seventeen".