21503345 has 16 divisors (see below), whose sum is σ = 27276480. Its totient is φ = 16228800.

The previous prime is 21503341. The next prime is 21503357. The reversal of 21503345 is 54330512.

It is not a de Polignac number, because 21503345 - 2² = 21503341 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21503345.

It is not an unprimeable number, because it can be changed into a prime (21503341) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 43550 + ... + 44040.

It is an arithmetic number, because the mean of its divisors is an integer number (1704780).

Almost surely, 2^21503345 is an apocalyptic number.

It is an amenable number.

21503345 is a deficient number, since it is larger than the sum of its proper divisors (5773135).

21503345 is a wasteful number, since it uses less digits than its factorization.

21503345 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 976.

The product of its (nonzero) digits is 1800, while the sum is 23.

The square root of 21503345 is about 4637.1699343457. The cubic root of 21503345 is about 278.0793081527.

Adding to 21503345 its reverse (54330512), we get a palindrome (75833857).

The spelling of 21503345 in words is "twenty-one million, five hundred three thousand, three hundred forty-five".