21789541 has 4 divisors (see below), whose sum is σ = 21848332. Its totient is φ = 21730752.

The previous prime is 21789511. The next prime is 21789557. The reversal of 21789541 is 14598712.

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 16402500 + 5387041 = 4050^2 + 2321^2 .

It is a cyclic number.

It is not a de Polignac number, because 21789541 - 2¹⁹ = 21265253 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 21789541.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21789511) 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, 28836 + ... + 29581.

It is an arithmetic number, because the mean of its divisors is an integer number (5462083).

Almost surely, 2^21789541 is an apocalyptic number.

It is an amenable number.

21789541 is a deficient number, since it is larger than the sum of its proper divisors (58791).

21789541 is an equidigital number, since it uses as much as digits as its factorization.

21789541 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58790.

The product of its digits is 20160, while the sum is 37.

The square root of 21789541 is about 4667.9268417575. The cubic root of 21789541 is about 279.3075619764.

The spelling of 21789541 in words is "twenty-one million, seven hundred eighty-nine thousand, five hundred forty-one".