21166541 has 4 divisors (see below), whose sum is σ = 23090784. Its totient is φ = 19242300.

The previous prime is 21166529. The next prime is 21166559. The reversal of 21166541 is 14566112.

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 not a de Polignac number, because 21166541 - 2¹⁸ = 20904397 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21166541.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21166511) 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, 962105 + ... + 962126.

It is an arithmetic number, because the mean of its divisors is an integer number (5772696).

Almost surely, 2^21166541 is an apocalyptic number.

It is an amenable number.

21166541 is a deficient number, since it is larger than the sum of its proper divisors (1924243).

21166541 is a wasteful number, since it uses less digits than its factorization.

21166541 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1924242.

The product of its digits is 1440, while the sum is 26.

The square root of 21166541 is about 4600.7109233248. The cubic root of 21166541 is about 276.6198219102.

The spelling of 21166541 in words is "twenty-one million, one hundred sixty-six thousand, five hundred forty-one".