21520493 has 2 divisors, whose sum is σ = 21520494. Its totient is φ = 21520492.

The previous prime is 21520481. The next prime is 21520507. The reversal of 21520493 is 39402512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21362884 + 157609 = 4622^2 + 397^2 .

It is a cyclic number.

It is not a de Polignac number, because 21520493 - 2¹⁰ = 21519469 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21520423) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760246 + 10760247.

It is an arithmetic number, because the mean of its divisors is an integer number (10760247).

Almost surely, 2^21520493 is an apocalyptic number.

It is an amenable number.

21520493 is a deficient number, since it is larger than the sum of its proper divisors (1).

21520493 is an equidigital number, since it uses as much as digits as its factorization.

21520493 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2160, while the sum is 26.

The square root of 21520493 is about 4639.0185384411. The cubic root of 21520493 is about 278.1532073062.

The spelling of 21520493 in words is "twenty-one million, five hundred twenty thousand, four hundred ninety-three".