21681073 has 8 divisors (see below), whose sum is σ = 22492448. Its totient is φ = 20883744.

The previous prime is 21681061. The next prime is 21681091. The reversal of 21681073 is 37018612.

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 21681073 - 2¹³ = 21672881 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21681173) 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 in 7 ways as a sum of consecutive naturals, for example, 315 + ... + 6592.

It is an arithmetic number, because the mean of its divisors is an integer number (2811556).

Almost surely, 2^21681073 is an apocalyptic number.

It is an amenable number.

21681073 is a deficient number, since it is larger than the sum of its proper divisors (811375).

21681073 is an equidigital number, since it uses as much as digits as its factorization.

21681073 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7023.

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 21681073 is about 4656.2939125446. The cubic root of 21681073 is about 278.8433278894.

Adding to 21681073 its reverse (37018612), we get a palindrome (58699685).

The spelling of 21681073 in words is "twenty-one million, six hundred eighty-one thousand, seventy-three".