21604347 has 8 divisors (see below), whose sum is σ = 32006480. Its totient is φ = 14402880.

The previous prime is 21604339. The next prime is 21604369. The reversal of 21604347 is 74340612.

21604347 is a `hidden beast` number, since 21 + 604 + 34 + 7 = 666.

It is not a de Polignac number, because 21604347 - 2³ = 21604339 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 800161 = 21604347 / (2 + 1 + 6 + 0 + 4 + 3 + 4 + 7).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21604347.

It is not an unprimeable number, because it can be changed into a prime (21604327) 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, 400054 + ... + 400107.

It is an arithmetic number, because the mean of its divisors is an integer number (4000810).

Almost surely, 2^21604347 is an apocalyptic number.

21604347 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21604347 is a deficient number, since it is larger than the sum of its proper divisors (10402133).

21604347 is an equidigital number, since it uses as much as digits as its factorization.

21604347 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 800170 (or 800164 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 27.

The square root of 21604347 is about 4648.0476546610. The cubic root of 21604347 is about 278.5140111587.

Adding to 21604347 its reverse (74340612), we get a palindrome (95944959).

The spelling of 21604347 in words is "twenty-one million, six hundred four thousand, three hundred forty-seven".