21138253 has 2 divisors, whose sum is σ = 21138254. Its totient is φ = 21138252.

The previous prime is 21138251. The next prime is 21138277. The reversal of 21138253 is 35283112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19027044 + 2111209 = 4362^2 + 1453^2 .

It is a cyclic number.

It is not a de Polignac number, because 21138253 - 2¹ = 21138251 is a prime.

Together with 21138251, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21138251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10569126 + 10569127.

It is an arithmetic number, because the mean of its divisors is an integer number (10569127).

Almost surely, 2^21138253 is an apocalyptic number.

It is an amenable number.

21138253 is a deficient number, since it is larger than the sum of its proper divisors (1).

21138253 is an equidigital number, since it uses as much as digits as its factorization.

21138253 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1440, while the sum is 25.

The square root of 21138253 is about 4597.6355879952. The cubic root of 21138253 is about 276.4965375558.

The spelling of 21138253 in words is "twenty-one million, one hundred thirty-eight thousand, two hundred fifty-three".