21251055 has 48 divisors (see below), whose sum is σ = 40957920. Its totient is φ = 9370368.

The previous prime is 21251053. The next prime is 21251077. The reversal of 21251055 is 55015212.

It is not a de Polignac number, because 21251055 - 2¹ = 21251053 is a prime.

It is a super-2 number, since 2×21251055² = 903214677226050, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21251053) 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 47 ways as a sum of consecutive naturals, for example, 20817 + ... + 21813.

It is an arithmetic number, because the mean of its divisors is an integer number (853290).

Almost surely, 2^21251055 is an apocalyptic number.

21251055 is a deficient number, since it is larger than the sum of its proper divisors (19706865).

21251055 is a wasteful number, since it uses less digits than its factorization.

21251055 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1048 (or 1041 counting only the distinct ones).

The product of its (nonzero) digits is 500, while the sum is 21.

The square root of 21251055 is about 4609.8866580427. The cubic root of 21251055 is about 276.9874965575.

Adding to 21251055 its reverse (55015212), we get a palindrome (76266267).

The spelling of 21251055 in words is "twenty-one million, two hundred fifty-one thousand, fifty-five".