21641347 has 16 divisors (see below), whose sum is σ = 26817280. Its totient is φ = 17006112.

The previous prime is 21641311. The next prime is 21641353. The reversal of 21641347 is 74314612.

It is a 6-Lehmer number, since φ(21641347) divides (21641347-1)⁶.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21641347 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21641387) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14104 + ... + 15562.

It is an arithmetic number, because the mean of its divisors is an integer number (1676080).

Almost surely, 2^21641347 is an apocalyptic number.

21641347 is a deficient number, since it is larger than the sum of its proper divisors (5175933).

21641347 is a wasteful number, since it uses less digits than its factorization.

21641347 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1642.

The product of its digits is 4032, while the sum is 28.

The square root of 21641347 is about 4652.0261177255. The cubic root of 21641347 is about 278.6729165424.

Adding to 21641347 its reverse (74314612), we get a palindrome (95955959).

The spelling of 21641347 in words is "twenty-one million, six hundred forty-one thousand, three hundred forty-seven".