21521849 has 2 divisors, whose sum is σ = 21521850. Its totient is φ = 21521848.

The previous prime is 21521839. The next prime is 21521893. The reversal of 21521849 is 94812512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12730624 + 8791225 = 3568^2 + 2965^2 .

It is a cyclic number.

It is not a de Polignac number, because 21521849 - 2⁴ = 21521833 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21521839) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760924 + 10760925.

It is an arithmetic number, because the mean of its divisors is an integer number (10760925).

Almost surely, 2^21521849 is an apocalyptic number.

It is an amenable number.

21521849 is a deficient number, since it is larger than the sum of its proper divisors (1).

21521849 is an equidigital number, since it uses as much as digits as its factorization.

21521849 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5760, while the sum is 32.

The square root of 21521849 is about 4639.1646877428. The cubic root of 21521849 is about 278.1590493010.

The spelling of 21521849 in words is "twenty-one million, five hundred twenty-one thousand, eight hundred forty-nine".