21032861 has 4 divisors (see below), whose sum is σ = 21377724. Its totient is φ = 20688000.

The previous prime is 21032857. The next prime is 21032863. The reversal of 21032861 is 16823012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3308761 + 17724100 = 1819^2 + 4210^2 .

It is a cyclic number.

It is not a de Polignac number, because 21032861 - 2² = 21032857 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21032863) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 172340 + ... + 172461.

It is an arithmetic number, because the mean of its divisors is an integer number (5344431).

Almost surely, 2^21032861 is an apocalyptic number.

It is an amenable number.

21032861 is a deficient number, since it is larger than the sum of its proper divisors (344863).

21032861 is an equidigital number, since it uses as much as digits as its factorization.

21032861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 344862.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21032861 is about 4586.1597224693. The cubic root of 21032861 is about 276.0362490022.

Adding to 21032861 its reverse (16823012), we get a palindrome (37855873).

The spelling of 21032861 in words is "twenty-one million, thirty-two thousand, eight hundred sixty-one".