21081653 has 4 divisors (see below), whose sum is σ = 21571968. Its totient is φ = 20591340.

The previous prime is 21081647. The next prime is 21081673. The reversal of 21081653 is 35618012.

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 a cyclic number.

It is not a de Polignac number, because 21081653 - 2⁶ = 21081589 is a prime.

It is a super-3 number, since 3×21081653³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21081623) 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, 245093 + ... + 245178.

It is an arithmetic number, because the mean of its divisors is an integer number (5392992).

Almost surely, 2^21081653 is an apocalyptic number.

It is an amenable number.

21081653 is a deficient number, since it is larger than the sum of its proper divisors (490315).

21081653 is an equidigital number, since it uses as much as digits as its factorization.

21081653 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 490314.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 21081653 is about 4591.4761242982. The cubic root of 21081653 is about 276.2495336560.

Adding to 21081653 its reverse (35618012), we get a palindrome (56699665).

The spelling of 21081653 in words is "twenty-one million, eighty-one thousand, six hundred fifty-three".