21563081 has 8 divisors (see below), whose sum is σ = 23226720. Its totient is φ = 19952352.

The previous prime is 21563077. The next prime is 21563093. The reversal of 21563081 is 18036512.

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 21563081 - 2² = 21563077 is a prime.

It is a super-2 number, since 2×21563081² = 929932924425122, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21563081.

It is not an unprimeable number, because it can be changed into a prime (21563041) 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, 12380 + ... + 14013.

It is an arithmetic number, because the mean of its divisors is an integer number (2903340).

Almost surely, 2^21563081 is an apocalyptic number.

It is an amenable number.

21563081 is a deficient number, since it is larger than the sum of its proper divisors (1663639).

21563081 is a wasteful number, since it uses less digits than its factorization.

21563081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26455.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 21563081 is about 4643.6064648073. The cubic root of 21563081 is about 278.3365702549.

Adding to 21563081 its reverse (18036512), we get a palindrome (39599593).

The spelling of 21563081 in words is "twenty-one million, five hundred sixty-three thousand, eighty-one".