21753481 has 4 divisors (see below), whose sum is σ = 21968964. Its totient is φ = 21538000.

The previous prime is 21753419. The next prime is 21753533. The reversal of 21753481 is 18435712.

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

It can be written as a sum of positive squares in 2 ways, for example, as 13395600 + 8357881 = 3660^2 + 2891^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21753481 is a prime.

It is a super-2 number, since 2×21753481² = 946427871234722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21750481) 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, 107590 + ... + 107791.

It is an arithmetic number, because the mean of its divisors is an integer number (5492241).

Almost surely, 2^21753481 is an apocalyptic number.

It is an amenable number.

21753481 is a deficient number, since it is larger than the sum of its proper divisors (215483).

21753481 is a wasteful number, since it uses less digits than its factorization.

21753481 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 215482.

The product of its digits is 6720, while the sum is 31.

The square root of 21753481 is about 4664.0627139866. The cubic root of 21753481 is about 279.1533994537.

The spelling of 21753481 in words is "twenty-one million, seven hundred fifty-three thousand, four hundred eighty-one".