21720443 has 8 divisors (see below), whose sum is σ = 22384128. Its totient is φ = 21060864.

The previous prime is 21720431. The next prime is 21720463. The reversal of 21720443 is 34402712.

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 21720443 - 2⁴ = 21720427 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21720463) 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, 12230 + ... + 13892.

It is an arithmetic number, because the mean of its divisors is an integer number (2798016).

Almost surely, 2^21720443 is an apocalyptic number.

21720443 is a deficient number, since it is larger than the sum of its proper divisors (663685).

21720443 is a wasteful number, since it uses less digits than its factorization.

21720443 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2053.

The product of its (nonzero) digits is 1344, while the sum is 23.

The square root of 21720443 is about 4660.5196062242. The cubic root of 21720443 is about 279.0120068658.

The spelling of 21720443 in words is "twenty-one million, seven hundred twenty thousand, four hundred forty-three".