21570145 has 4 divisors (see below), whose sum is σ = 25884180. Its totient is φ = 17256112.

The previous prime is 21570139. The next prime is 21570163. The reversal of 21570145 is 54107512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 17172736 + 4397409 = 4144^2 + 2097^2 .

It is a cyclic number.

It is not a de Polignac number, because 21570145 - 2³ = 21570137 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2157010 + ... + 2157019.

It is an arithmetic number, because the mean of its divisors is an integer number (6471045).

Almost surely, 2^21570145 is an apocalyptic number.

It is an amenable number.

21570145 is a deficient number, since it is larger than the sum of its proper divisors (4314035).

21570145 is an equidigital number, since it uses as much as digits as its factorization.

21570145 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4314034.

The product of its (nonzero) digits is 1400, while the sum is 25.

The square root of 21570145 is about 4644.3670182276. The cubic root of 21570145 is about 278.3669610089.

Adding to 21570145 its reverse (54107512), we get a palindrome (75677657).

The spelling of 21570145 in words is "twenty-one million, five hundred seventy thousand, one hundred forty-five".