21730081 has 4 divisors (see below), whose sum is σ = 21901312. Its totient is φ = 21558852.

The previous prime is 21730067. The next prime is 21730099. The reversal of 21730081 is 18003712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21730081 - 2⁹ = 21729569 is a prime.

It is a super-2 number, since 2×21730081² = 944392840533122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21730001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 85425 + ... + 85678.

It is an arithmetic number, because the mean of its divisors is an integer number (5475328).

Almost surely, 2^21730081 is an apocalyptic number.

It is an amenable number.

21730081 is a deficient number, since it is larger than the sum of its proper divisors (171231).

21730081 is a wasteful number, since it uses less digits than its factorization.

21730081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 171230.

The product of its (nonzero) digits is 336, while the sum is 22.

The square root of 21730081 is about 4661.5534964216. The cubic root of 21730081 is about 279.0532693771.

Adding to 21730081 its reverse (18003712), we get a palindrome (39733793).

The spelling of 21730081 in words is "twenty-one million, seven hundred thirty thousand, eighty-one".