21551347 has 4 divisors (see below), whose sum is σ = 21641760. Its totient is φ = 21460936.

The previous prime is 21551323. The next prime is 21551351. The reversal of 21551347 is 74315512.

It is a happy number.

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 21551347 - 2¹¹ = 21549299 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21551317) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 44848 + ... + 45325.

It is an arithmetic number, because the mean of its divisors is an integer number (5410440).

Almost surely, 2^21551347 is an apocalyptic number.

21551347 is a deficient number, since it is larger than the sum of its proper divisors (90413).

21551347 is an equidigital number, since it uses as much as digits as its factorization.

21551347 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90412.

The product of its digits is 4200, while the sum is 28.

The square root of 21551347 is about 4642.3428352503. The cubic root of 21551347 is about 278.2860735453.

Adding to 21551347 its reverse (74315512), we get a palindrome (95866859).

It can be divided in two parts, 21 and 551347, that added together give a cube (551368 = 82³).

The spelling of 21551347 in words is "twenty-one million, five hundred fifty-one thousand, three hundred forty-seven".