21660225 has 12 divisors (see below), whose sum is σ = 35811696. Its totient is φ = 11552080.

The previous prime is 21660211. The next prime is 21660239. The reversal of 21660225 is 52206612.

It is an interprime number because it is at equal distance from previous prime (21660211) and next prime (21660239).

It is not a de Polignac number, because 21660225 - 2⁶ = 21660161 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21660195 and 21660204.

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, 144327 + ... + 144476.

It is an arithmetic number, because the mean of its divisors is an integer number (2984308).

Almost surely, 2^21660225 is an apocalyptic number.

21660225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21660225 is a deficient number, since it is larger than the sum of its proper divisors (14151471).

21660225 is a wasteful number, since it uses less digits than its factorization.

21660225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 288816 (or 288811 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 21660225 is about 4654.0546838214. The cubic root of 21660225 is about 278.7539228737.

Adding to 21660225 its reverse (52206612), we get a palindrome (73866837).

The spelling of 21660225 in words is "twenty-one million, six hundred sixty thousand, two hundred twenty-five".