21040643 has 8 divisors (see below), whose sum is σ = 22744848. Its totient is φ = 19348704.

The previous prime is 21040633. The next prime is 21040651. The reversal of 21040643 is 34604012.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21040643 - 2⁴ = 21040627 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21040633) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 680 + ... + 6522.

It is an arithmetic number, because the mean of its divisors is an integer number (2843106).

Almost surely, 2^21040643 is an apocalyptic number.

21040643 is a deficient number, since it is larger than the sum of its proper divisors (1704205).

21040643 is a wasteful number, since it uses less digits than its factorization.

21040643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6133.

The product of its (nonzero) digits is 576, while the sum is 20.

The square root of 21040643 is about 4587.0080662672. The cubic root of 21040643 is about 276.0702885814.

Adding to 21040643 its reverse (34604012), we get a palindrome (55644655).

The spelling of 21040643 in words is "twenty-one million, forty thousand, six hundred forty-three".