21142445 has 4 divisors (see below), whose sum is σ = 25370940. Its totient is φ = 16913952.

The previous prime is 21142439. The next prime is 21142447. The reversal of 21142445 is 54424112.

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 7739524 + 13402921 = 2782^2 + 3661^2 .

It is a cyclic number.

It is not a de Polignac number, because 21142445 - 2²⁰ = 20093869 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21142445.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21142447) 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 3 ways as a sum of consecutive naturals, for example, 2114240 + ... + 2114249.

It is an arithmetic number, because the mean of its divisors is an integer number (6342735).

Almost surely, 2^21142445 is an apocalyptic number.

It is an amenable number.

21142445 is a deficient number, since it is larger than the sum of its proper divisors (4228495).

21142445 is an equidigital number, since it uses as much as digits as its factorization.

21142445 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4228494.

The product of its digits is 1280, while the sum is 23.

The square root of 21142445 is about 4598.0914518961. The cubic root of 21142445 is about 276.5148140090.

Adding to 21142445 its reverse (54424112), we get a palindrome (75566557).

The spelling of 21142445 in words is "twenty-one million, one hundred forty-two thousand, four hundred forty-five".