21087145 has 8 divisors (see below), whose sum is σ = 25651656. Its totient is φ = 16638336.

The previous prime is 21087137. The next prime is 21087149. The reversal of 21087145 is 54178012.

It can be written as a sum of positive squares in 4 ways, for example, as 28224 + 21058921 = 168^2 + 4589^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21087145 - 2³ = 21087137 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21087149) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28522 + ... + 29251.

It is an arithmetic number, because the mean of its divisors is an integer number (3206457).

Almost surely, 2^21087145 is an apocalyptic number.

It is an amenable number.

21087145 is a deficient number, since it is larger than the sum of its proper divisors (4564511).

21087145 is an equidigital number, since it uses as much as digits as its factorization.

21087145 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57851.

The product of its (nonzero) digits is 2240, while the sum is 28.

The square root of 21087145 is about 4592.0741500982. The cubic root of 21087145 is about 276.2735202431.

The spelling of 21087145 in words is "twenty-one million, eighty-seven thousand, one hundred forty-five".