21057547 has 4 divisors (see below), whose sum is σ = 24065776. Its totient is φ = 18049320.

The previous prime is 21057541. The next prime is 21057563. The reversal of 21057547 is 74575012.

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 21057547 - 2⁷ = 21057419 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21057541) 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, 1504104 + ... + 1504117.

It is an arithmetic number, because the mean of its divisors is an integer number (6016444).

Almost surely, 2^21057547 is an apocalyptic number.

21057547 is a deficient number, since it is larger than the sum of its proper divisors (3008229).

21057547 is an equidigital number, since it uses as much as digits as its factorization.

21057547 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3008228.

The product of its (nonzero) digits is 9800, while the sum is 31.

The square root of 21057547 is about 4588.8502917398. The cubic root of 21057547 is about 276.1442001848.

The spelling of 21057547 in words is "twenty-one million, fifty-seven thousand, five hundred forty-seven".