21405005689 has 4 divisors (see below), whose sum is σ = 21405300624. Its totient is φ = 21404710756.

The previous prime is 21405005659. The next prime is 21405005701. The reversal of 21405005689 is 98650050412.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21405005689 - 2³³ = 12815071097 is a prime.

It is a super-2 number, since 2×21405005689² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21405005659) 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, 46014 + ... + 211960.

It is an arithmetic number, because the mean of its divisors is an integer number (5351325156).

Almost surely, 2^21405005689 is an apocalyptic number.

It is an amenable number.

21405005689 is a deficient number, since it is larger than the sum of its proper divisors (294935).

21405005689 is a wasteful number, since it uses less digits than its factorization.

21405005689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 294934.

The product of its (nonzero) digits is 86400, while the sum is 40.

The spelling of 21405005689 in words is "twenty-one billion, four hundred five million, five thousand, six hundred eighty-nine".