21718125 has 120 divisors (see below), whose sum is σ = 47759712. Its totient is φ = 9720000.

The previous prime is 21718087. The next prime is 21718133. The reversal of 21718125 is 52181712.

It is not a de Polignac number, because 21718125 - 2⁹ = 21717613 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

Its product of digits (1120) is a multiple of the sum of its prime divisors (32).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

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 119 ways as a sum of consecutive naturals, for example, 1670619 + ... + 1670631.

Almost surely, 2^21718125 is an apocalyptic number.

21718125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21718125 is an abundant number, since it is smaller than the sum of its proper divisors (26041587).

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

21718125 is an equidigital number, since it uses as much as digits as its factorization.

21718125 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59 (or 32 counting only the distinct ones).

The product of its digits is 1120, while the sum is 27.

The square root of 21718125 is about 4660.2709148718. The cubic root of 21718125 is about 279.0020811499.

Adding to 21718125 its reverse (52181712), we get a palindrome (73899837).

It can be divided in two parts, 2171 and 8125, that added together give a triangular number (10296 = T₁₄₃).

The spelling of 21718125 in words is "twenty-one million, seven hundred eighteen thousand, one hundred twenty-five".