21054861 has 6 divisors (see below), whose sum is σ = 30412590. Its totient is φ = 14036568.

The previous prime is 21054851. The next prime is 21054863. The reversal of 21054861 is 16845012.

It can be written as a sum of positive squares in only one way, i.e., 10692900 + 10361961 = 3270^2 + 3219^2 .

It is not a de Polignac number, because 21054861 - 2¹⁵ = 21022093 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21054863) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1169706 + ... + 1169723.

It is an arithmetic number, because the mean of its divisors is an integer number (5068765).

Almost surely, 2^21054861 is an apocalyptic number.

It is an amenable number.

21054861 is a deficient number, since it is larger than the sum of its proper divisors (9357729).

21054861 is a wasteful number, since it uses less digits than its factorization.

21054861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2339435 (or 2339432 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 21054861 is about 4588.5576165065. The cubic root of 21054861 is about 276.1324584743.

Adding to 21054861 its reverse (16845012), we get a palindrome (37899873).

The spelling of 21054861 in words is "twenty-one million, fifty-four thousand, eight hundred sixty-one".