21605293 has 2 divisors, whose sum is σ = 21605294. Its totient is φ = 21605292.

The previous prime is 21605267. The next prime is 21605321. The reversal of 21605293 is 39250612.

It is an a-pointer prime, because the next prime (21605321) can be obtained adding 21605293 to its sum of digits (28).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21511044 + 94249 = 4638^2 + 307^2 .

It is a cyclic number.

It is not a de Polignac number, because 21605293 - 2²¹ = 19508141 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21605263) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10802646 + 10802647.

It is an arithmetic number, because the mean of its divisors is an integer number (10802647).

Almost surely, 2^21605293 is an apocalyptic number.

It is an amenable number.

21605293 is a deficient number, since it is larger than the sum of its proper divisors (1).

21605293 is an equidigital number, since it uses as much as digits as its factorization.

21605293 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3240, while the sum is 28.

The square root of 21605293 is about 4648.1494167034. The cubic root of 21605293 is about 278.5180762420.

The spelling of 21605293 in words is "twenty-one million, six hundred five thousand, two hundred ninety-three".