21006181 has 8 divisors (see below), whose sum is σ = 24197120. Its totient is φ = 17862768.

The previous prime is 21006163. The next prime is 21006217. The reversal of 21006181 is 18160012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21006181 - 2⁷ = 21006053 is a prime.

It is a super-2 number, since 2×21006181² = 882519280409522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21006151) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10926 + ... + 12703.

It is an arithmetic number, because the mean of its divisors is an integer number (3024640).

Almost surely, 2^21006181 is an apocalyptic number.

It is an amenable number.

21006181 is a deficient number, since it is larger than the sum of its proper divisors (3190939).

21006181 is a wasteful number, since it uses less digits than its factorization.

21006181 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23763.

The product of its (nonzero) digits is 96, while the sum is 19.

The square root of 21006181 is about 4583.2500477281. The cubic root of 21006181 is about 275.9194830945.

Adding to 21006181 its reverse (18160012), we get a palindrome (39166193).

It can be divided in two parts, 2100 and 6181, that added together give a square (8281 = 91²).

The spelling of 21006181 in words is "twenty-one million, six thousand, one hundred eighty-one".