21731107 has 4 divisors (see below), whose sum is σ = 22261176. Its totient is φ = 21201040.

The previous prime is 21731089. The next prime is 21731111. The reversal of 21731107 is 70113712.

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

It is a cyclic number.

It is not a de Polignac number, because 21731107 - 2⁷ = 21730979 is a prime.

It is a super-2 number, since 2×21731107² = 944482022890898, which contains 22 as substring.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21731147) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 264973 + ... + 265054.

It is an arithmetic number, because the mean of its divisors is an integer number (5565294).

Almost surely, 2^21731107 is an apocalyptic number.

21731107 is a deficient number, since it is larger than the sum of its proper divisors (530069).

21731107 is an equidigital number, since it uses as much as digits as its factorization.

21731107 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 530068.

The product of its (nonzero) digits is 294, while the sum is 22.

The square root of 21731107 is about 4661.6635442726. The cubic root of 21731107 is about 279.0576612023.

Adding to 21731107 its reverse (70113712), we get a palindrome (91844819).

The spelling of 21731107 in words is "twenty-one million, seven hundred thirty-one thousand, one hundred seven".