21055539 has 4 divisors (see below), whose sum is σ = 28074056. Its totient is φ = 14037024.

The previous prime is 21055513. The next prime is 21055543. The reversal of 21055539 is 93555012.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21055539 - 2¹¹ = 21053491 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21055579) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3509254 + ... + 3509259.

It is an arithmetic number, because the mean of its divisors is an integer number (7018514).

Almost surely, 2^21055539 is an apocalyptic number.

21055539 is a deficient number, since it is larger than the sum of its proper divisors (7018517).

21055539 is an equidigital number, since it uses as much as digits as its factorization.

21055539 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7018516.

The product of its (nonzero) digits is 6750, while the sum is 30.

The square root of 21055539 is about 4588.6314953371. The cubic root of 21055539 is about 276.1354224105.

The spelling of 21055539 in words is "twenty-one million, fifty-five thousand, five hundred thirty-nine".