21169821 has 8 divisors (see below), whose sum is σ = 29453760. Its totient is φ = 13499552.

The previous prime is 21169783. The next prime is 21169823. The reversal of 21169821 is 12896112.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21169821 is a prime.

It is a super-2 number, since 2×21169821² = 896322642344082, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21169823) 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 7 ways as a sum of consecutive naturals, for example, 153336 + ... + 153473.

It is an arithmetic number, because the mean of its divisors is an integer number (3681720).

Almost surely, 2^21169821 is an apocalyptic number.

It is an amenable number.

21169821 is a deficient number, since it is larger than the sum of its proper divisors (8283939).

21169821 is a wasteful number, since it uses less digits than its factorization.

21169821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 306835.

The product of its digits is 1728, while the sum is 30.

The square root of 21169821 is about 4601.0673761639. The cubic root of 21169821 is about 276.6341096510.

The spelling of 21169821 in words is "twenty-one million, one hundred sixty-nine thousand, eight hundred twenty-one".