21665073 has 16 divisors (see below), whose sum is σ = 31057920. Its totient is φ = 13390416.

The previous prime is 21665071. The next prime is 21665087. The reversal of 21665073 is 37056612.

It is not a de Polignac number, because 21665073 - 2¹ = 21665071 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21665073.

It is not an unprimeable number, because it can be changed into a prime (21665071) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1365 + ... + 6722.

It is an arithmetic number, because the mean of its divisors is an integer number (1941120).

Almost surely, 2^21665073 is an apocalyptic number.

It is an amenable number.

21665073 is a deficient number, since it is larger than the sum of its proper divisors (9392847).

21665073 is a wasteful number, since it uses less digits than its factorization.

21665073 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8156.

The product of its (nonzero) digits is 7560, while the sum is 30.

The square root of 21665073 is about 4654.5754908477. The cubic root of 21665073 is about 278.7747182595.

The spelling of 21665073 in words is "twenty-one million, six hundred sixty-five thousand, seventy-three".