21860081 has 4 divisors (see below), whose sum is σ = 22450932. Its totient is φ = 21269232.

The previous prime is 21860077. The next prime is 21860099. The reversal of 21860081 is 18006812.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13104400 + 8755681 = 3620^2 + 2959^2 .

It is a cyclic number.

It is not a de Polignac number, because 21860081 - 2² = 21860077 is a prime.

It is a super-2 number, since 2×21860081² = 955726282653122, 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 21860081.

It is not an unprimeable number, because it can be changed into a prime (21860381) 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, 295370 + ... + 295443.

It is an arithmetic number, because the mean of its divisors is an integer number (5612733).

Almost surely, 2^21860081 is an apocalyptic number.

It is an amenable number.

21860081 is a deficient number, since it is larger than the sum of its proper divisors (590851).

21860081 is an equidigital number, since it uses as much as digits as its factorization.

21860081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 590850.

The product of its (nonzero) digits is 768, while the sum is 26.

The square root of 21860081 is about 4675.4765532510. The cubic root of 21860081 is about 279.6086411738.

Adding to 21860081 its reverse (18006812), we get a palindrome (39866893).

The spelling of 21860081 in words is "twenty-one million, eight hundred sixty thousand, eighty-one".