21130725 has 48 divisors (see below), whose sum is σ = 43568640. Its totient is φ = 8779200.

The previous prime is 21130699. The next prime is 21130727. The reversal of 21130725 is 52703112.

It is not a de Polignac number, because 21130725 - 2⁷ = 21130597 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21130727) by changing a digit.

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 47 ways as a sum of consecutive naturals, for example, 3946 + ... + 7604.

It is an arithmetic number, because the mean of its divisors is an integer number (907680).

Almost surely, 2^21130725 is an apocalyptic number.

21130725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21130725 is an abundant number, since it is smaller than the sum of its proper divisors (22437915).

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

21130725 is a wasteful number, since it uses less digits than its factorization.

21130725 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3690 (or 3685 counting only the distinct ones).

The product of its (nonzero) digits is 420, while the sum is 21.

The square root of 21130725 is about 4596.8168334185. The cubic root of 21130725 is about 276.4637106066.

Adding to 21130725 its reverse (52703112), we get a palindrome (73833837).

The spelling of 21130725 in words is "twenty-one million, one hundred thirty thousand, seven hundred twenty-five".