21756473 has 4 divisors (see below), whose sum is σ = 21767760. Its totient is φ = 21745188.

The previous prime is 21756461. The next prime is 21756487. The reversal of 21756473 is 37465712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21756473 - 2⁴ = 21756457 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21756403) 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, 1943 + ... + 6876.

It is an arithmetic number, because the mean of its divisors is an integer number (5441940).

Almost surely, 2^21756473 is an apocalyptic number.

It is an amenable number.

21756473 is a deficient number, since it is larger than the sum of its proper divisors (11287).

21756473 is an equidigital number, since it uses as much as digits as its factorization.

21756473 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11286.

The product of its digits is 35280, while the sum is 35.

The square root of 21756473 is about 4664.3834533623. The cubic root of 21756473 is about 279.1661972320.

The spelling of 21756473 in words is "twenty-one million, seven hundred fifty-six thousand, four hundred seventy-three".