21353491 has 2 divisors, whose sum is σ = 21353492. Its totient is φ = 21353490.

The previous prime is 21353461. The next prime is 21353531. The reversal of 21353491 is 19435312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21353491 - 2⁵ = 21353459 is a prime.

It is not a weakly prime, because it can be changed into another prime (21353401) 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, 10676745 + 10676746.

It is an arithmetic number, because the mean of its divisors is an integer number (10676746).

Almost surely, 2^21353491 is an apocalyptic number.

21353491 is a deficient number, since it is larger than the sum of its proper divisors (1).

21353491 is an equidigital number, since it uses as much as digits as its factorization.

21353491 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21353491 is about 4620.9837697183. The cubic root of 21353491 is about 277.4318356506.

The spelling of 21353491 in words is "twenty-one million, three hundred fifty-three thousand, four hundred ninety-one".