21861081 has 24 divisors (see below), whose sum is σ = 34594560. Its totient is φ = 13192800.

The previous prime is 21861079. The next prime is 21861083. The reversal of 21861081 is 18016812.

It is an interprime number because it is at equal distance from previous prime (21861079) and next prime (21861083).

It is not a de Polignac number, because 21861081 - 2¹ = 21861079 is a prime.

It is a super-2 number, since 2×21861081² = 955813724977122, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21861083) 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 23 ways as a sum of consecutive naturals, for example, 45400 + ... + 45878.

It is an arithmetic number, because the mean of its divisors is an integer number (1441440).

Almost surely, 2^21861081 is an apocalyptic number.

It is an amenable number.

21861081 is a deficient number, since it is larger than the sum of its proper divisors (12733479).

21861081 is a wasteful number, since it uses less digits than its factorization.

21861081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 957 (or 954 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 27.

The square root of 21861081 is about 4675.5834929985. The cubic root of 21861081 is about 279.6129047198.

Adding to 21861081 its reverse (18016812), we get a palindrome (39877893).

The spelling of 21861081 in words is "twenty-one million, eight hundred sixty-one thousand, eighty-one".