21403643 has 2 divisors, whose sum is σ = 21403644.
Its totient is φ = 21403642.
The previous prime is 21403621. The next prime is 21403667. The reversal of 21403643 is 34630412.
It is a happy number.
It is a weak prime.
It is a cyclic number.
It is not a de Polignac number, because 21403643 - 26 = 21403579 is a prime.
It is a Sophie Germain prime.
It is not a weakly prime, because it can be changed into another prime (21403243) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10701821 + 10701822.
It is an arithmetic number, because the mean of its divisors is an integer number (10701822).
Almost surely, 221403643 is an apocalyptic number.
21403643 is a deficient number, since it is larger than the sum of its proper divisors (1).
21403643 is an equidigital number, since it uses as much as digits as its factorization.
21403643 is an evil number, because the sum of its binary digits is even.
The product of its (nonzero) digits is 1728, while the sum is 23.
The square root of 21403643 is about 4626.4071372935.
The cubic root of 21403643 is about 277.6488631261.
The spelling of 21403643 in words is "twenty-one million, four hundred three thousand, six hundred forty-three".