21011225 has 24 divisors (see below), whose sum is σ = 27390360. Its totient is φ = 15966720.

The previous prime is 21011191. The next prime is 21011231. The reversal of 21011225 is 52211012.

It can be written as a sum of positive squares in 12 ways, for example, as 3211264 + 17799961 = 1792^2 + 4219^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21011225 is a prime.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 52727 + ... + 53123.

It is an arithmetic number, because the mean of its divisors is an integer number (1141265).

Almost surely, 2^21011225 is an apocalyptic number.

21011225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21011225 is a deficient number, since it is larger than the sum of its proper divisors (6379135).

21011225 is a wasteful number, since it uses less digits than its factorization.

21011225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 509 (or 504 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 14.

The square root of 21011225 is about 4583.8002792443. The cubic root of 21011225 is about 275.9415659042.

Adding to 21011225 its reverse (52211012), we get a palindrome (73222237).

The spelling of 21011225 in words is "twenty-one million, eleven thousand, two hundred twenty-five".