21400493 has 2 divisors, whose sum is σ = 21400494. Its totient is φ = 21400492.

The previous prime is 21400487. The next prime is 21400507. The reversal of 21400493 is 39400412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20994724 + 405769 = 4582^2 + 637^2 .

It is a cyclic number.

It is not a de Polignac number, because 21400493 - 2⁶ = 21400429 is a prime.

It is a super-2 number, since 2×21400493² = 915962201286098, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21400453) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10700246 + 10700247.

It is an arithmetic number, because the mean of its divisors is an integer number (10700247).

Almost surely, 2^21400493 is an apocalyptic number.

It is an amenable number.

21400493 is a deficient number, since it is larger than the sum of its proper divisors (1).

21400493 is an equidigital number, since it uses as much as digits as its factorization.

21400493 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 864, while the sum is 23.

The square root of 21400493 is about 4626.0666878029. The cubic root of 21400493 is about 277.6352418183.

The spelling of 21400493 in words is "twenty-one million, four hundred thousand, four hundred ninety-three".