21720466 has 4 divisors (see below), whose sum is σ = 32580702. Its totient is φ = 10860232.

The previous prime is 21720463. The next prime is 21720467. The reversal of 21720466 is 66402712.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 11703241 + 10017225 = 3421^2 + 3165^2 .

It is not an unprimeable number, because it can be changed into a prime (21720463) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5430115 + ... + 5430118.

Almost surely, 2^21720466 is an apocalyptic number.

21720466 is a deficient number, since it is larger than the sum of its proper divisors (10860236).

21720466 is a wasteful number, since it uses less digits than its factorization.

21720466 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10860235.

The product of its (nonzero) digits is 4032, while the sum is 28.

The square root of 21720466 is about 4660.5220737595. The cubic root of 21720466 is about 279.0121053487.

The spelling of 21720466 in words is "twenty-one million, seven hundred twenty thousand, four hundred sixty-six".