21066831 has 8 divisors (see below), whose sum is σ = 31210160. Its totient is φ = 14044536.

The previous prime is 21066823. The next prime is 21066833. The reversal of 21066831 is 13866012.

It is not a de Polignac number, because 21066831 - 2³ = 21066823 is a prime.

It is a super-2 number, since 2×21066831² = 887622736765122, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 780253 = 21066831 / (2 + 1 + 0 + 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 = 21066795 and 21066804.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21066833) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 390100 + ... + 390153.

It is an arithmetic number, because the mean of its divisors is an integer number (3901270).

Almost surely, 2^21066831 is an apocalyptic number.

21066831 is a deficient number, since it is larger than the sum of its proper divisors (10143329).

21066831 is an equidigital number, since it uses as much as digits as its factorization.

21066831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 780262 (or 780256 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21066831 is about 4589.8617626242. The cubic root of 21066831 is about 276.1847770237.

The spelling of 21066831 in words is "twenty-one million, sixty-six thousand, eight hundred thirty-one".