21945253 has 4 divisors (see below), whose sum is σ = 23940288. Its totient is φ = 19950220.

The previous prime is 21945239. The next prime is 21945263. The reversal of 21945253 is 35254912.

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 21945253 - 2¹³ = 21937061 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21945263) 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, 997501 + ... + 997522.

It is an arithmetic number, because the mean of its divisors is an integer number (5985072).

Almost surely, 2^21945253 is an apocalyptic number.

It is an amenable number.

21945253 is a deficient number, since it is larger than the sum of its proper divisors (1995035).

21945253 is a wasteful number, since it uses less digits than its factorization.

21945253 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1995034.

The product of its digits is 10800, while the sum is 31.

The square root of 21945253 is about 4684.5760747372. The cubic root of 21945253 is about 279.9713108361.

It can be divided in two parts, 2194 and 5253, that added together give a palindrome (7447).

The spelling of 21945253 in words is "twenty-one million, nine hundred forty-five thousand, two hundred fifty-three".