21606025 has 24 divisors (see below), whose sum is σ = 30793664. Its totient is φ = 14731200.

The previous prime is 21606023. The next prime is 21606037. The reversal of 21606025 is 52060612.

It is not a de Polignac number, because 21606025 - 2¹ = 21606023 is a prime.

It is a Duffinian number.

It is a zygodrome in base 3.

It is a junction number, because it is equal to n+sod(n) for n = 21605987 and 21606005.

It is not an unprimeable number, because it can be changed into a prime (21606023) 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, 57739 + ... + 58111.

Almost surely, 2^21606025 is an apocalyptic number.

21606025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21606025 is a deficient number, since it is larger than the sum of its proper divisors (9187639).

21606025 is a wasteful number, since it uses less digits than its factorization.

21606025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 721 (or 716 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 21606025 is about 4648.2281570508. The cubic root of 21606025 is about 278.5212216584.

Adding to 21606025 its reverse (52060612), we get a palindrome (73666637).

The spelling of 21606025 in words is "twenty-one million, six hundred six thousand, twenty-five".