21403145 has 4 divisors (see below), whose sum is σ = 25683780. Its totient is φ = 17122512.

The previous prime is 21403117. The next prime is 21403159. The reversal of 21403145 is 54130412.

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 11182336 + 10220809 = 3344^2 + 3197^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21403145 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, 2140310 + ... + 2140319.

It is an arithmetic number, because the mean of its divisors is an integer number (6420945).

Almost surely, 2^21403145 is an apocalyptic number.

It is an amenable number.

21403145 is a deficient number, since it is larger than the sum of its proper divisors (4280635).

21403145 is an equidigital number, since it uses as much as digits as its factorization.

21403145 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4280634.

The product of its (nonzero) digits is 480, while the sum is 20.

The square root of 21403145 is about 4626.3533155175. The cubic root of 21403145 is about 277.6467097511.

Adding to 21403145 its reverse (54130412), we get a palindrome (75533557).

The spelling of 21403145 in words is "twenty-one million, four hundred three thousand, one hundred forty-five".