21550643 has 2 divisors, whose sum is σ = 21550644. Its totient is φ = 21550642.

The previous prime is 21550637. The next prime is 21550657. The reversal of 21550643 is 34605512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21550643 - 2⁸ = 21550387 is a prime.

It is not a weakly prime, because it can be changed into another prime (21550043) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10775321 + 10775322.

It is an arithmetic number, because the mean of its divisors is an integer number (10775322).

Almost surely, 2^21550643 is an apocalyptic number.

21550643 is a deficient number, since it is larger than the sum of its proper divisors (1).

21550643 is an equidigital number, since it uses as much as digits as its factorization.

21550643 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3600, while the sum is 26.

The square root of 21550643 is about 4642.2670108472. The cubic root of 21550643 is about 278.2830433321.

The spelling of 21550643 in words is "twenty-one million, five hundred fifty thousand, six hundred forty-three".