21266831 has 4 divisors (see below), whose sum is σ = 22000200. Its totient is φ = 20533464.

The previous prime is 21266807. The next prime is 21266849. The reversal of 21266831 is 13866212.

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-21266831 is a prime.

It is a super-2 number, since 2×21266831² = 904556201565122, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (29), and also a Moran number because the ratio is a prime number: 733339 = 21266831 / (2 + 1 + 2 + 6 + 6 + 8 + 3 + 1).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21266794 and 21266803.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21266891) 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, 366641 + ... + 366698.

It is an arithmetic number, because the mean of its divisors is an integer number (5500050).

Almost surely, 2^21266831 is an apocalyptic number.

21266831 is a deficient number, since it is larger than the sum of its proper divisors (733369).

21266831 is an equidigital number, since it uses as much as digits as its factorization.

21266831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 733368.

The product of its digits is 3456, while the sum is 29.

The square root of 21266831 is about 4611.5974455713. The cubic root of 21266831 is about 277.0560213731.

The spelling of 21266831 in words is "twenty-one million, two hundred sixty-six thousand, eight hundred thirty-one".