21000075 has 12 divisors (see below), whose sum is σ = 34720248. Its totient is φ = 11200000.

The previous prime is 21000059. The next prime is 21000097. The reversal of 21000075 is 57000012.

It is a happy number.

It is not a de Polignac number, because 21000075 - 2⁴ = 21000059 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 139926 + ... + 140075.

It is an arithmetic number, because the mean of its divisors is an integer number (2893354).

Almost surely, 2^21000075 is an apocalyptic number.

21000075 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21000075 is a deficient number, since it is larger than the sum of its proper divisors (13720173).

21000075 is a wasteful number, since it uses less digits than its factorization.

21000075 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 280014 (or 280009 counting only the distinct ones).

The product of its (nonzero) digits is 70, while the sum is 15.

The square root of 21000075 is about 4582.5838781194. The cubic root of 21000075 is about 275.8927460811.

Adding to 21000075 its reverse (57000012), we get a palindrome (78000087).

It can be divided in two parts, 2100007 and 5, that added together give a palindrome (2100012).

The spelling of 21000075 in words is "twenty-one million, seventy-five", and thus it is an aban number and an uban number.