21551725 has 18 divisors (see below), whose sum is σ = 28943646. Its totient is φ = 15912000.

The previous prime is 21551701. The next prime is 21551737. The reversal of 21551725 is 52715512.

It can be written as a sum of positive squares in 9 ways, for example, as 20097289 + 1454436 = 4483^2 + 1206^2 .

It is not a de Polignac number, because 21551725 - 2⁵ = 21551693 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21551693 and 21551702.

It is a congruent number.

It is an unprimeable number.

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 17 ways as a sum of consecutive naturals, for example, 1675 + ... + 6775.

Almost surely, 2^21551725 is an apocalyptic number.

21551725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21551725 is a deficient number, since it is larger than the sum of its proper divisors (7391921).

21551725 is a wasteful number, since it uses less digits than its factorization.

21551725 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5137 (or 5119 counting only the distinct ones).

The product of its digits is 3500, while the sum is 28.

The square root of 21551725 is about 4642.3835472740. The cubic root of 21551725 is about 278.2877005360.

The spelling of 21551725 in words is "twenty-one million, five hundred fifty-one thousand, seven hundred twenty-five".