21545725 has 6 divisors (see below), whose sum is σ = 26716730. Its totient is φ = 17236560.

The previous prime is 21545723. The next prime is 21545759. The reversal of 21545725 is 52754512.

It can be written as a sum of positive squares in 3 ways, for example, as 6661561 + 14884164 = 2581^2 + 3858^2 .

It is not a de Polignac number, because 21545725 - 2¹ = 21545723 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21545723) 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 5 ways as a sum of consecutive naturals, for example, 430890 + ... + 430939.

Almost surely, 2^21545725 is an apocalyptic number.

21545725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21545725 is a deficient number, since it is larger than the sum of its proper divisors (5171005).

21545725 is an equidigital number, since it uses as much as digits as its factorization.

21545725 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 861839 (or 861834 counting only the distinct ones).

The product of its digits is 14000, while the sum is 31.

The square root of 21545725 is about 4641.7372825269. The cubic root of 21545725 is about 278.2618730415.

The spelling of 21545725 in words is "twenty-one million, five hundred forty-five thousand, seven hundred twenty-five".