21634253 has 2 divisors, whose sum is σ = 21634254. Its totient is φ = 21634252.

The previous prime is 21634213. The next prime is 21634259. The reversal of 21634253 is 35243612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16630084 + 5004169 = 4078^2 + 2237^2 .

It is a cyclic number.

It is not a de Polignac number, because 21634253 - 2²⁴ = 4857037 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21634259) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10817126 + 10817127.

It is an arithmetic number, because the mean of its divisors is an integer number (10817127).

Almost surely, 2^21634253 is an apocalyptic number.

It is an amenable number.

21634253 is a deficient number, since it is larger than the sum of its proper divisors (1).

21634253 is an equidigital number, since it uses as much as digits as its factorization.

21634253 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4320, while the sum is 26.

The square root of 21634253 is about 4651.2635917565. The cubic root of 21634253 is about 278.6424636980.

Adding to 21634253 its reverse (35243612), we get a palindrome (56877865).

The spelling of 21634253 in words is "twenty-one million, six hundred thirty-four thousand, two hundred fifty-three".