21293521 has 2 divisors, whose sum is σ = 21293522. Its totient is φ = 21293520.

The previous prime is 21293483. The next prime is 21293563. The reversal of 21293521 is 12539212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12173121 + 9120400 = 3489^2 + 3020^2 .

It is a cyclic number.

It is not a de Polignac number, because 21293521 - 2¹⁹ = 20769233 is a prime.

It is not a weakly prime, because it can be changed into another prime (21291521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10646760 + 10646761.

It is an arithmetic number, because the mean of its divisors is an integer number (10646761).

Almost surely, 2^21293521 is an apocalyptic number.

It is an amenable number.

21293521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21293521 is an equidigital number, since it uses as much as digits as its factorization.

21293521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1080, while the sum is 25.

The square root of 21293521 is about 4614.4903293863. The cubic root of 21293521 is about 277.1718752417.

The spelling of 21293521 in words is "twenty-one million, two hundred ninety-three thousand, five hundred twenty-one".