21453681 has 4 divisors (see below), whose sum is σ = 28604912. Its totient is φ = 14302452.

The previous prime is 21453671. The next prime is 21453683. The reversal of 21453681 is 18635412.

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.

It is not a de Polignac number, because 21453681 - 2²² = 17259377 is a prime.

It is a super-2 number, since 2×21453681² = 920520856899522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21453683) 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, 3575611 + ... + 3575616.

It is an arithmetic number, because the mean of its divisors is an integer number (7151228).

Almost surely, 2^21453681 is an apocalyptic number.

It is an amenable number.

21453681 is a deficient number, since it is larger than the sum of its proper divisors (7151231).

21453681 is an equidigital number, since it uses as much as digits as its factorization.

21453681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7151230.

The product of its digits is 5760, while the sum is 30.

The square root of 21453681 is about 4631.8118485103. The cubic root of 21453681 is about 277.8650596770.

The spelling of 21453681 in words is "twenty-one million, four hundred fifty-three thousand, six hundred eighty-one".