21405653 has 2 divisors, whose sum is σ = 21405654. Its totient is φ = 21405652.

The previous prime is 21405641. The next prime is 21405661. The reversal of 21405653 is 35650412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16834609 + 4571044 = 4103^2 + 2138^2 .

It is a cyclic number.

It is not a de Polignac number, because 21405653 - 2⁶ = 21405589 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21405623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10702826 + 10702827.

It is an arithmetic number, because the mean of its divisors is an integer number (10702827).

Almost surely, 2^21405653 is an apocalyptic number.

It is an amenable number.

21405653 is a deficient number, since it is larger than the sum of its proper divisors (1).

21405653 is an equidigital number, since it uses as much as digits as its factorization.

21405653 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3600, while the sum is 26.

The square root of 21405653 is about 4626.6243633993. The cubic root of 21405653 is about 277.6575541193.

The spelling of 21405653 in words is "twenty-one million, four hundred five thousand, six hundred fifty-three".