21755047 has 4 divisors (see below), whose sum is σ = 22017240. Its totient is φ = 21492856.

The previous prime is 21755021. The next prime is 21755077. The reversal of 21755047 is 74055712.

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 21755047 - 2¹¹ = 21752999 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21755077) 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, 130972 + ... + 131137.

It is an arithmetic number, because the mean of its divisors is an integer number (5504310).

Almost surely, 2^21755047 is an apocalyptic number.

21755047 is a deficient number, since it is larger than the sum of its proper divisors (262193).

21755047 is an equidigital number, since it uses as much as digits as its factorization.

21755047 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 262192.

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

The square root of 21755047 is about 4664.2305903546. The cubic root of 21755047 is about 279.1600979024.

The spelling of 21755047 in words is "twenty-one million, seven hundred fifty-five thousand, forty-seven".