21388541 has 2 divisors, whose sum is σ = 21388542. Its totient is φ = 21388540.

The previous prime is 21388529. The next prime is 21388559. The reversal of 21388541 is 14588312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15405625 + 5982916 = 3925^2 + 2446^2 .

It is a cyclic number.

It is not a de Polignac number, because 21388541 - 2¹⁴ = 21372157 is a prime.

It is a super-2 number, since 2×21388541² = 914939372217362, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21388498 and 21388507.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21388441) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10694270 + 10694271.

It is an arithmetic number, because the mean of its divisors is an integer number (10694271).

Almost surely, 2^21388541 is an apocalyptic number.

It is an amenable number.

21388541 is a deficient number, since it is larger than the sum of its proper divisors (1).

21388541 is an equidigital number, since it uses as much as digits as its factorization.

21388541 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7680, while the sum is 32.

The square root of 21388541 is about 4624.7746972150. The cubic root of 21388541 is about 277.5835465240.

The spelling of 21388541 in words is "twenty-one million, three hundred eighty-eight thousand, five hundred forty-one".