21605311357 has 8 divisors (see below), whose sum is σ = 24702684800. Its totient is φ = 18510663024.

The previous prime is 21605311327. The next prime is 21605311361. The reversal of 21605311357 is 75311350612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21605311357 - 2¹¹ = 21605309309 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 (21605311327) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 664257 + ... + 696022.

It is an arithmetic number, because the mean of its divisors is an integer number (3087835600).

Almost surely, 2^21605311357 is an apocalyptic number.

It is an amenable number.

21605311357 is a deficient number, since it is larger than the sum of its proper divisors (3097373443).

21605311357 is a wasteful number, since it uses less digits than its factorization.

21605311357 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1362555.

The product of its (nonzero) digits is 18900, while the sum is 34.

Adding to 21605311357 its reverse (75311350612), we get a palindrome (96916661969).

The spelling of 21605311357 in words is "twenty-one billion, six hundred five million, three hundred eleven thousand, three hundred fifty-seven".