21931055 has 4 divisors (see below), whose sum is σ = 26317272. Its totient is φ = 17544840.

The previous prime is 21931033. The next prime is 21931057. The reversal of 21931055 is 55013912.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21931055 - 2⁶ = 21930991 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21931057) 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 3 ways as a sum of consecutive naturals, for example, 2193101 + ... + 2193110.

It is an arithmetic number, because the mean of its divisors is an integer number (6579318).

Almost surely, 2^21931055 is an apocalyptic number.

21931055 is a deficient number, since it is larger than the sum of its proper divisors (4386217).

21931055 is an equidigital number, since it uses as much as digits as its factorization.

21931055 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4386216.

The product of its (nonzero) digits is 1350, while the sum is 26.

The square root of 21931055 is about 4683.0604309575. The cubic root of 21931055 is about 279.9109197920.

Adding to 21931055 its reverse (55013912), we get a palindrome (76944967).

The spelling of 21931055 in words is "twenty-one million, nine hundred thirty-one thousand, fifty-five".