21012861 has 8 divisors (see below), whose sum is σ = 28355040. Its totient is φ = 13839632.

The previous prime is 21012851. The next prime is 21012877. The reversal of 21012861 is 16821012.

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

It is a cyclic number.

It is not a de Polignac number, because 21012861 - 2⁵ = 21012829 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012821) 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 7 ways as a sum of consecutive naturals, for example, 41946 + ... + 42443.

It is an arithmetic number, because the mean of its divisors is an integer number (3544380).

Almost surely, 2^21012861 is an apocalyptic number.

It is an amenable number.

21012861 is a deficient number, since it is larger than the sum of its proper divisors (7342179).

21012861 is an equidigital number, since it uses as much as digits as its factorization.

21012861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 84475.

The product of its (nonzero) digits is 192, while the sum is 21.

The square root of 21012861 is about 4583.9787303171. The cubic root of 21012861 is about 275.9487276108.

Adding to 21012861 its reverse (16821012), we get a palindrome (37833873).

The spelling of 21012861 in words is "twenty-one million, twelve thousand, eight hundred sixty-one".