21106643 has 2 divisors, whose sum is σ = 21106644. Its totient is φ = 21106642.

The previous prime is 21106607. The next prime is 21106661. The reversal of 21106643 is 34660112.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21106643 - 2¹² = 21102547 is a prime.

It is not a weakly prime, because it can be changed into another prime (21106343) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10553321 + 10553322.

It is an arithmetic number, because the mean of its divisors is an integer number (10553322).

Almost surely, 2^21106643 is an apocalyptic number.

21106643 is a deficient number, since it is larger than the sum of its proper divisors (1).

21106643 is an equidigital number, since it uses as much as digits as its factorization.

21106643 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 864, while the sum is 23.

The square root of 21106643 is about 4594.1966653595. The cubic root of 21106643 is about 276.3586451169.

Adding to 21106643 its reverse (34660112), we get a palindrome (55766755).

The spelling of 21106643 in words is "twenty-one million, one hundred six thousand, six hundred forty-three".