21004861 has 4 divisors (see below), whose sum is σ = 22110400. Its totient is φ = 19899324.

The previous prime is 21004847. The next prime is 21004883. The reversal of 21004861 is 16840012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21004861 - 2⁵ = 21004829 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 (21004811) 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, 552741 + ... + 552778.

It is an arithmetic number, because the mean of its divisors is an integer number (5527600).

Almost surely, 2^21004861 is an apocalyptic number.

It is an amenable number.

21004861 is a deficient number, since it is larger than the sum of its proper divisors (1105539).

21004861 is a wasteful number, since it uses less digits than its factorization.

21004861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1105538.

The product of its (nonzero) digits is 384, while the sum is 22.

The square root of 21004861 is about 4583.1060428491. The cubic root of 21004861 is about 275.9137035044.

Adding to 21004861 its reverse (16840012), we get a palindrome (37844873).

The spelling of 21004861 in words is "twenty-one million, four thousand, eight hundred sixty-one".