21490643 has 2 divisors, whose sum is σ = 21490644. Its totient is φ = 21490642.

The previous prime is 21490627. The next prime is 21490663. The reversal of 21490643 is 34609412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21490643 - 2⁴ = 21490627 is a prime.

It is not a weakly prime, because it can be changed into another prime (21490603) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10745321 + 10745322.

It is an arithmetic number, because the mean of its divisors is an integer number (10745322).

Almost surely, 2^21490643 is an apocalyptic number.

21490643 is a deficient number, since it is larger than the sum of its proper divisors (1).

21490643 is an equidigital number, since it uses as much as digits as its factorization.

21490643 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5184, while the sum is 29.

The square root of 21490643 is about 4635.8001466845. The cubic root of 21490643 is about 278.0245436640.

The spelling of 21490643 in words is "twenty-one million, four hundred ninety thousand, six hundred forty-three".