21172575 has 24 divisors (see below), whose sum is σ = 35207568. Its totient is φ = 11226880.

The previous prime is 21172561. The next prime is 21172579. The reversal of 21172575 is 57527112.

It is not a de Polignac number, because 21172575 - 2¹⁰ = 21171551 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21172579) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 14059 + ... + 15491.

It is an arithmetic number, because the mean of its divisors is an integer number (1466982).

Almost surely, 2^21172575 is an apocalyptic number.

21172575 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21172575 is a deficient number, since it is larger than the sum of its proper divisors (14034993).

21172575 is a wasteful number, since it uses less digits than its factorization.

21172575 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1643 (or 1638 counting only the distinct ones).

The product of its digits is 4900, while the sum is 30.

The square root of 21172575 is about 4601.3666448133. The cubic root of 21172575 is about 276.6461049863.

Adding to 21172575 its reverse (57527112), we get a palindrome (78699687).

The spelling of 21172575 in words is "twenty-one million, one hundred seventy-two thousand, five hundred seventy-five".