21366131 has 4 divisors (see below), whose sum is σ = 21943632. Its totient is φ = 20788632.

The previous prime is 21366113. The next prime is 21366133. The reversal of 21366131 is 13166312.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21366131 is a prime.

It is a super-2 number, since 2×21366131² = 913023107818322, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21366097 and 21366106.

It is not an unprimeable number, because it can be changed into a prime (21366133) 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, 288695 + ... + 288768.

It is an arithmetic number, because the mean of its divisors is an integer number (5485908).

Almost surely, 2^21366131 is an apocalyptic number.

21366131 is a deficient number, since it is larger than the sum of its proper divisors (577501).

21366131 is an equidigital number, since it uses as much as digits as its factorization.

21366131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 577500.

The product of its digits is 648, while the sum is 23.

The square root of 21366131 is about 4622.3512415220. The cubic root of 21366131 is about 277.4865659162.

The spelling of 21366131 in words is "twenty-one million, three hundred sixty-six thousand, one hundred thirty-one".