21545345 has 4 divisors (see below), whose sum is σ = 25854420. Its totient is φ = 17236272.

The previous prime is 21545339. The next prime is 21545351. The reversal of 21545345 is 54354512.

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

It is an interprime number because it is at equal distance from previous prime (21545339) and next prime (21545351).

It can be written as a sum of positive squares in 2 ways, for example, as 9042049 + 12503296 = 3007^2 + 3536^2 .

It is a cyclic number.

It is not a de Polignac number, because 21545345 - 2²⁰ = 20496769 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, 2154530 + ... + 2154539.

It is an arithmetic number, because the mean of its divisors is an integer number (6463605).

Almost surely, 2^21545345 is an apocalyptic number.

It is an amenable number.

21545345 is a deficient number, since it is larger than the sum of its proper divisors (4309075).

21545345 is an equidigital number, since it uses as much as digits as its factorization.

21545345 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4309074.

The product of its digits is 12000, while the sum is 29.

The square root of 21545345 is about 4641.6963493964. The cubic root of 21545345 is about 278.2602371387.

Adding to 21545345 its reverse (54354512), we get a palindrome (75899857).

The spelling of 21545345 in words is "twenty-one million, five hundred forty-five thousand, three hundred forty-five".