21403645 has 8 divisors (see below), whose sum is σ = 25793280. Its totient is φ = 17050320.

The previous prime is 21403643. The next prime is 21403667. The reversal of 21403645 is 54630412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21403645 - 2¹ = 21403643 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21403643) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7761 + ... + 10150.

It is an arithmetic number, because the mean of its divisors is an integer number (3224160).

Almost surely, 2^21403645 is an apocalyptic number.

It is an amenable number.

21403645 is a deficient number, since it is larger than the sum of its proper divisors (4389635).

21403645 is a wasteful number, since it uses less digits than its factorization.

21403645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18155.

The product of its (nonzero) digits is 2880, while the sum is 25.

The square root of 21403645 is about 4626.4073534439. The cubic root of 21403645 is about 277.6488717741.

It can be divided in two parts, 2140364 and 5, that added together give a square (2140369 = 1463²).

The spelling of 21403645 in words is "twenty-one million, four hundred three thousand, six hundred forty-five".