21755747 has 4 divisors (see below), whose sum is σ = 23429280. Its totient is φ = 20082216.

The previous prime is 21755717. The next prime is 21755761. The reversal of 21755747 is 74755712.

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 21755747 - 2⁶ = 21755683 is a prime.

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 21755747.

It is not an unprimeable number, because it can be changed into a prime (21755717) 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, 836747 + ... + 836772.

It is an arithmetic number, because the mean of its divisors is an integer number (5857320).

Almost surely, 2^21755747 is an apocalyptic number.

21755747 is a deficient number, since it is larger than the sum of its proper divisors (1673533).

21755747 is a wasteful number, since it uses less digits than its factorization.

21755747 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1673532.

The product of its digits is 68600, while the sum is 38.

The square root of 21755747 is about 4664.3056289227. The cubic root of 21755747 is about 279.1630919965.

The spelling of 21755747 in words is "twenty-one million, seven hundred fifty-five thousand, seven hundred forty-seven".