21072345 has 16 divisors (see below), whose sum is σ = 38532480. Its totient is φ = 9633024.

The previous prime is 21072329. The next prime is 21072361. The reversal of 21072345 is 54327012.

It is an interprime number because it is at equal distance from previous prime (21072329) and next prime (21072361).

It is not a de Polignac number, because 21072345 - 2⁴ = 21072329 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is an unprimeable number.

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, 100240 + ... + 100449.

It is an arithmetic number, because the mean of its divisors is an integer number (2408280).

Almost surely, 2^21072345 is an apocalyptic number.

It is an amenable number.

21072345 is a deficient number, since it is larger than the sum of its proper divisors (17460135).

21072345 is a wasteful number, since it uses less digits than its factorization.

21072345 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 200704.

The product of its (nonzero) digits is 1680, while the sum is 24.

The square root of 21072345 is about 4590.4623950099. The cubic root of 21072345 is about 276.2088709815.

Adding to 21072345 its reverse (54327012), we get a palindrome (75399357).

The spelling of 21072345 in words is "twenty-one million, seventy-two thousand, three hundred forty-five".