21071730 has 16 divisors (see below), whose sum is σ = 50572224. Its totient is φ = 5619120.

The previous prime is 21071717. The next prime is 21071737. The reversal of 21071730 is 3717012.

It is a junction number, because it is equal to n+sod(n) for n = 21071697 and 21071706.

It is not an unprimeable number, because it can be changed into a prime (21071737) 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, 351166 + ... + 351225.

It is an arithmetic number, because the mean of its divisors is an integer number (3160764).

Almost surely, 2^21071730 is an apocalyptic number.

21071730 is an abundant number, since it is smaller than the sum of its proper divisors (29500494).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21071730 is a wasteful number, since it uses less digits than its factorization.

21071730 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 702401.

The product of its (nonzero) digits is 294, while the sum is 21.

The square root of 21071730 is about 4590.3954078053. The cubic root of 21071730 is about 276.2061838876.

Adding to 21071730 its reverse (3717012), we get a palindrome (24788742).

The spelling of 21071730 in words is "twenty-one million, seventy-one thousand, seven hundred thirty".