21372445 has 4 divisors (see below), whose sum is σ = 25646940. Its totient is φ = 17097952.

The previous prime is 21372437. The next prime is 21372469. The reversal of 21372445 is 54427312.

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 5067001 + 16305444 = 2251^2 + 4038^2 .

It is a cyclic number.

It is not a de Polignac number, because 21372445 - 2³ = 21372437 is a prime.

It is a congruent number.

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, 2137240 + ... + 2137249.

It is an arithmetic number, because the mean of its divisors is an integer number (6411735).

Almost surely, 2^21372445 is an apocalyptic number.

It is an amenable number.

21372445 is a deficient number, since it is larger than the sum of its proper divisors (4274495).

21372445 is an equidigital number, since it uses as much as digits as its factorization.

21372445 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4274494.

The product of its digits is 6720, while the sum is 28.

The square root of 21372445 is about 4623.0341768150. The cubic root of 21372445 is about 277.5138969855.

Adding to 21372445 its reverse (54427312), we get a palindrome (75799757).

The spelling of 21372445 in words is "twenty-one million, three hundred seventy-two thousand, four hundred forty-five".