21320331 has 4 divisors (see below), whose sum is σ = 28427112. Its totient is φ = 14213552.

The previous prime is 21320323. The next prime is 21320401. The reversal of 21320331 is 13302312.

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 21320331 - 2³ = 21320323 is a prime.

It is a super-2 number, since 2×21320331² = 909113027899122, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21320331.

It is not an unprimeable number, because it can be changed into a prime (21320311) 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, 3553386 + ... + 3553391.

It is an arithmetic number, because the mean of its divisors is an integer number (7106778).

Almost surely, 2^21320331 is an apocalyptic number.

21320331 is a deficient number, since it is larger than the sum of its proper divisors (7106781).

21320331 is an equidigital number, since it uses as much as digits as its factorization.

21320331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7106780.

The product of its (nonzero) digits is 108, while the sum is 15.

The square root of 21320331 is about 4617.3943951107. The cubic root of 21320331 is about 277.2881525740.

Adding to 21320331 its reverse (13302312), we get a palindrome (34622643).

The spelling of 21320331 in words is "twenty-one million, three hundred twenty thousand, three hundred thirty-one".