21781053 has 12 divisors (see below), whose sum is σ = 35956128. Its totient is φ = 12446280.

The previous prime is 21781021. The next prime is 21781093. The reversal of 21781053 is 35018712.

It is not a de Polignac number, because 21781053 - 2⁵ = 21781021 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21781093) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 172803 + ... + 172928.

It is an arithmetic number, because the mean of its divisors is an integer number (2996344).

Almost surely, 2^21781053 is an apocalyptic number.

It is an amenable number.

21781053 is a deficient number, since it is larger than the sum of its proper divisors (14175075).

21781053 is a wasteful number, since it uses less digits than its factorization.

21781053 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 345744 (or 345741 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 27.

The square root of 21781053 is about 4667.0175701405. The cubic root of 21781053 is about 279.2712896735.

Adding to 21781053 its reverse (35018712), we get a palindrome (56799765).

The spelling of 21781053 in words is "twenty-one million, seven hundred eighty-one thousand, fifty-three".