21331643 has 2 divisors, whose sum is σ = 21331644. Its totient is φ = 21331642.

The previous prime is 21331637. The next prime is 21331657. The reversal of 21331643 is 34613312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21331643 - 2²² = 17137339 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21331663) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10665821 + 10665822.

It is an arithmetic number, because the mean of its divisors is an integer number (10665822).

Almost surely, 2^21331643 is an apocalyptic number.

21331643 is a deficient number, since it is larger than the sum of its proper divisors (1).

21331643 is an equidigital number, since it uses as much as digits as its factorization.

21331643 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1296, while the sum is 23.

The square root of 21331643 is about 4618.6191659413. The cubic root of 21331643 is about 277.3371844738.

Adding to 21331643 its reverse (34613312), we get a palindrome (55944955).

The spelling of 21331643 in words is "twenty-one million, three hundred thirty-one thousand, six hundred forty-three".