21628331 has 4 divisors (see below), whose sum is σ = 21710832. Its totient is φ = 21545832.

The previous prime is 21628283. The next prime is 21628339. The reversal of 21628331 is 13382612.

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 21628331 - 2¹⁸ = 21366187 is a prime.

It is a super-2 number, since 2×21628331² = 935569403691122, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21628331.

It is not an unprimeable number, because it can be changed into a prime (21628339) 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, 40856 + ... + 41381.

It is an arithmetic number, because the mean of its divisors is an integer number (5427708).

Almost surely, 2^21628331 is an apocalyptic number.

21628331 is a deficient number, since it is larger than the sum of its proper divisors (82501).

21628331 is an equidigital number, since it uses as much as digits as its factorization.

21628331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 82500.

The product of its digits is 1728, while the sum is 26.

The square root of 21628331 is about 4650.6269469825. The cubic root of 21628331 is about 278.6170368705.

The spelling of 21628331 in words is "twenty-one million, six hundred twenty-eight thousand, three hundred thirty-one".