21523347 has 8 divisors (see below), whose sum is σ = 31886480. Its totient is φ = 14348880.

The previous prime is 21523339. The next prime is 21523351. The reversal of 21523347 is 74332512.

It is not a de Polignac number, because 21523347 - 2³ = 21523339 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: 797161 = 21523347 / (2 + 1 + 5 + 2 + 3 + 3 + 4 + 7).

It is a Duffinian number.

It is a nialpdrome in base 3 and base 9.

It is a zygodrome in base 3.

It is a self number, because there is not a number n which added to its sum of digits gives 21523347.

It is not an unprimeable number, because it can be changed into a prime (21523387) 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, 398554 + ... + 398607.

It is an arithmetic number, because the mean of its divisors is an integer number (3985810).

Almost surely, 2^21523347 is an apocalyptic number.

21523347 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21523347 is a deficient number, since it is larger than the sum of its proper divisors (10363133).

21523347 is an equidigital number, since it uses as much as digits as its factorization.

21523347 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 797170 (or 797164 counting only the distinct ones).

The product of its digits is 5040, while the sum is 27.

The square root of 21523347 is about 4639.3261364125. The cubic root of 21523347 is about 278.1655027829.

Adding to 21523347 its reverse (74332512), we get a palindrome (95855859).

The spelling of 21523347 in words is "twenty-one million, five hundred twenty-three thousand, three hundred forty-seven".