21125181 has 32 divisors (see below), whose sum is σ = 35481600. Its totient is φ = 10860480.

The previous prime is 21125177. The next prime is 21125183. The reversal of 21125181 is 18152112.

It is not a de Polignac number, because 21125181 - 2² = 21125177 is a prime.

It is a super-2 number, since 2×21125181² = 892546544565522, which contains 22 as substring.

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

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21125183) 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 31 ways as a sum of consecutive naturals, for example, 24760 + ... + 25598.

It is an arithmetic number, because the mean of its divisors is an integer number (1108800).

Almost surely, 2^21125181 is an apocalyptic number.

21125181 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21125181 is a deficient number, since it is larger than the sum of its proper divisors (14356419).

21125181 is a wasteful number, since it uses less digits than its factorization.

21125181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 969.

The product of its digits is 160, while the sum is 21.

The square root of 21125181 is about 4596.2137678746. The cubic root of 21125181 is about 276.4395301951.

Adding to 21125181 its reverse (18152112), we get a palindrome (39277293).

The spelling of 21125181 in words is "twenty-one million, one hundred twenty-five thousand, one hundred eighty-one".