21648541 has 2 divisors, whose sum is σ = 21648542. Its totient is φ = 21648540.

The previous prime is 21648503. The next prime is 21648551. The reversal of 21648541 is 14584612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21427641 + 220900 = 4629^2 + 470^2 .

It is a cyclic number.

It is not a de Polignac number, because 21648541 - 2¹⁷ = 21517469 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21648551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10824270 + 10824271.

It is an arithmetic number, because the mean of its divisors is an integer number (10824271).

Almost surely, 2^21648541 is an apocalyptic number.

It is an amenable number.

21648541 is a deficient number, since it is larger than the sum of its proper divisors (1).

21648541 is an equidigital number, since it uses as much as digits as its factorization.

21648541 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7680, while the sum is 31.

The square root of 21648541 is about 4652.7992649587. The cubic root of 21648541 is about 278.7037918673.

The spelling of 21648541 in words is "twenty-one million, six hundred forty-eight thousand, five hundred forty-one".