21316557 has 8 divisors (see below), whose sum is σ = 28505376. Its totient is φ = 14169392.

The previous prime is 21316553. The next prime is 21316579. The reversal of 21316557 is 75561312.

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

It is a cyclic number.

It is not a de Polignac number, because 21316557 - 2² = 21316553 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21316553) 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, 9198 + ... + 11279.

It is an arithmetic number, because the mean of its divisors is an integer number (3563172).

Almost surely, 2^21316557 is an apocalyptic number.

It is an amenable number.

21316557 is a deficient number, since it is larger than the sum of its proper divisors (7188819).

21316557 is a wasteful number, since it uses less digits than its factorization.

21316557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20827.

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

The square root of 21316557 is about 4616.9857049811. The cubic root of 21316557 is about 277.2717903008.

Adding to 21316557 its reverse (75561312), we get a palindrome (96877869).

The spelling of 21316557 in words is "twenty-one million, three hundred sixteen thousand, five hundred fifty-seven".