21000735 has 64 divisors (see below), whose sum is σ = 43407360. Its totient is φ = 9434880.

The previous prime is 21000731. The next prime is 21000737. The reversal of 21000735 is 53700012.

It is not a de Polignac number, because 21000735 - 2² = 21000731 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000731) 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 63 ways as a sum of consecutive naturals, for example, 66939 + ... + 67251.

It is an arithmetic number, because the mean of its divisors is an integer number (678240).

Almost surely, 2^21000735 is an apocalyptic number.

21000735 is an abundant number, since it is smaller than the sum of its proper divisors (22406625).

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

21000735 is a wasteful number, since it uses less digits than its factorization.

21000735 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 405 (or 399 counting only the distinct ones).

The product of its (nonzero) digits is 210, while the sum is 18.

The square root of 21000735 is about 4582.6558893288. The cubic root of 21000735 is about 275.8956363454.

Adding to 21000735 its reverse (53700012), we get a palindrome (74700747).

The spelling of 21000735 in words is "twenty-one million, seven hundred thirty-five", and thus it is an aban number.