21612347 has 4 divisors (see below), whose sum is σ = 21656856. Its totient is φ = 21567840.

The previous prime is 21612319. The next prime is 21612373. The reversal of 21612347 is 74321612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21612347 - 2⁸ = 21612091 is a prime.

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

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21612317) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21518 + ... + 22499.

It is an arithmetic number, because the mean of its divisors is an integer number (5414214).

Almost surely, 2^21612347 is an apocalyptic number.

21612347 is a deficient number, since it is larger than the sum of its proper divisors (44509).

21612347 is an equidigital number, since it uses as much as digits as its factorization.

21612347 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44508.

The product of its digits is 2016, while the sum is 26.

The square root of 21612347 is about 4648.9081513835. The cubic root of 21612347 is about 278.5483844436.

Adding to 21612347 its reverse (74321612), we get a palindrome (95933959).

The spelling of 21612347 in words is "twenty-one million, six hundred twelve thousand, three hundred forty-seven".