21371565 has 8 divisors (see below), whose sum is σ = 34194528. Its totient is φ = 11398160.

The previous prime is 21371551. The next prime is 21371569. The reversal of 21371565 is 56517312.

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

It is not a de Polignac number, because 21371565 - 2⁷ = 21371437 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21371569) 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, 712371 + ... + 712400.

It is an arithmetic number, because the mean of its divisors is an integer number (4274316).

Almost surely, 2^21371565 is an apocalyptic number.

It is an amenable number.

21371565 is a deficient number, since it is larger than the sum of its proper divisors (12822963).

21371565 is a wasteful number, since it uses less digits than its factorization.

21371565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1424779.

The product of its digits is 6300, while the sum is 30.

The square root of 21371565 is about 4622.9390002465. The cubic root of 21371565 is about 277.5100881001.

Adding to 21371565 its reverse (56517312), we get a palindrome (77888877).

The spelling of 21371565 in words is "twenty-one million, three hundred seventy-one thousand, five hundred sixty-five".