21253541 has 8 divisors (see below), whose sum is σ = 22650624. Its totient is φ = 19895920.

The previous prime is 21253537. The next prime is 21253543. The reversal of 21253541 is 14535212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21253541 - 2² = 21253537 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21253543) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8750 + ... + 10911.

It is an arithmetic number, because the mean of its divisors is an integer number (2831328).

Almost surely, 2^21253541 is an apocalyptic number.

It is an amenable number.

21253541 is a deficient number, since it is larger than the sum of its proper divisors (1397083).

21253541 is a wasteful number, since it uses less digits than its factorization.

21253541 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19731.

The product of its digits is 1200, while the sum is 23.

The square root of 21253541 is about 4610.1562880232. The cubic root of 21253541 is about 276.9982970263.

Adding to 21253541 its reverse (14535212), we get a palindrome (35788753).

The spelling of 21253541 in words is "twenty-one million, two hundred fifty-three thousand, five hundred forty-one".