21718025 has 18 divisors (see below), whose sum is σ = 31328910. Its totient is φ = 14891520.

The previous prime is 21717989. The next prime is 21718033. The reversal of 21718025 is 52081712.

It can be written as a sum of positive squares in 3 ways, for example, as 2393209 + 19324816 = 1547^2 + 4396^2 .

It is not a de Polignac number, because 21718025 - 2⁶ = 21717961 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21717985 and 21718003.

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 7640 + ... + 10089.

It is an arithmetic number, because the mean of its divisors is an integer number (1740495).

Almost surely, 2^21718025 is an apocalyptic number.

21718025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21718025 is a deficient number, since it is larger than the sum of its proper divisors (9610885).

21718025 is a wasteful number, since it uses less digits than its factorization.

21718025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17753 (or 17741 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 26.

The square root of 21718025 is about 4660.2601858695. The cubic root of 21718025 is about 279.0016529323.

Adding to 21718025 its reverse (52081712), we get a palindrome (73799737).

The spelling of 21718025 in words is "twenty-one million, seven hundred eighteen thousand, twenty-five".