21305693 has 4 divisors (see below), whose sum is σ = 21433440. Its totient is φ = 21177948.

The previous prime is 21305689. The next prime is 21305699. The reversal of 21305693 is 39650312.

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 21305693 - 2² = 21305689 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 (21305699) 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, 63623 + ... + 63956.

It is an arithmetic number, because the mean of its divisors is an integer number (5358360).

Almost surely, 2^21305693 is an apocalyptic number.

It is an amenable number.

21305693 is a deficient number, since it is larger than the sum of its proper divisors (127747).

21305693 is a wasteful number, since it uses less digits than its factorization.

21305693 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127746.

The product of its (nonzero) digits is 4860, while the sum is 29.

The square root of 21305693 is about 4615.8090298451. The cubic root of 21305693 is about 277.2246783679.

The spelling of 21305693 in words is "twenty-one million, three hundred five thousand, six hundred ninety-three".