21053547 has 8 divisors (see below), whose sum is σ = 31190480. Its totient is φ = 14035680.

The previous prime is 21053537. The next prime is 21053563. The reversal of 21053547 is 74535012.

It is a happy number.

It is not a de Polignac number, because 21053547 - 2¹⁹ = 20529259 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: 779761 = 21053547 / (2 + 1 + 0 + 5 + 3 + 5 + 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 21053547.

It is not an unprimeable number, because it can be changed into a prime (21053537) 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, 389854 + ... + 389907.

It is an arithmetic number, because the mean of its divisors is an integer number (3898810).

Almost surely, 2^21053547 is an apocalyptic number.

21053547 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21053547 is a deficient number, since it is larger than the sum of its proper divisors (10136933).

21053547 is an equidigital number, since it uses as much as digits as its factorization.

21053547 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 779770 (or 779764 counting only the distinct ones).

The product of its (nonzero) digits is 4200, while the sum is 27.

The square root of 21053547 is about 4588.4144320233. The cubic root of 21053547 is about 276.1267140273.

Adding to 21053547 its reverse (74535012), we get a palindrome (95588559).

The spelling of 21053547 in words is "twenty-one million, fifty-three thousand, five hundred forty-seven".