21021673 has 8 divisors (see below), whose sum is σ = 22374792. Its totient is φ = 19681536.

The previous prime is 21021667. The next prime is 21021683. The reversal of 21021673 is 37612012.

It can be written as a sum of positive squares in 4 ways, for example, as 17952169 + 3069504 = 4237^2 + 1752^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21021673 is a prime.

It is a super-4 number, since 4×21021673⁴ (a number of 30 digits) contains 4444 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21021653) 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 7 ways as a sum of consecutive naturals, for example, 211 + ... + 6487.

It is an arithmetic number, because the mean of its divisors is an integer number (2796849).

Almost surely, 2^21021673 is an apocalyptic number.

It is an amenable number.

21021673 is a deficient number, since it is larger than the sum of its proper divisors (1353119).

21021673 is a wasteful number, since it uses less digits than its factorization.

21021673 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6491.

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 21021673 is about 4584.9398033126. The cubic root of 21021673 is about 275.9872963767.

Adding to 21021673 its reverse (37612012), we get a palindrome (58633685).

The spelling of 21021673 in words is "twenty-one million, twenty-one thousand, six hundred seventy-three".