21612345 has 8 divisors (see below), whose sum is σ = 34579776. Its totient is φ = 11526576.

The previous prime is 21612319. The next prime is 21612373. The reversal of 21612345 is 54321612.

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

It is not a de Polignac number, because 21612345 - 2⁵ = 21612313 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 (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 720397 + ... + 720426.

It is an arithmetic number, because the mean of its divisors is an integer number (4322472).

Almost surely, 2^21612345 is an apocalyptic number.

It is an amenable number.

21612345 is a deficient number, since it is larger than the sum of its proper divisors (12967431).

21612345 is a wasteful number, since it uses less digits than its factorization.

21612345 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1440831.

The product of its digits is 1440, while the sum is 24.

The square root of 21612345 is about 4648.9079362792. The cubic root of 21612345 is about 278.5483758514.

Adding to 21612345 its reverse (54321612), we get a palindrome (75933957).

It can be divided in two parts, 216 and 12345, that added together give a triangular number (12561 = T₁₅₈).

The spelling of 21612345 in words is "twenty-one million, six hundred twelve thousand, three hundred forty-five".