21408733 has 2 divisors, whose sum is σ = 21408734. Its totient is φ = 21408732.

The previous prime is 21408727. The next prime is 21408781. The reversal of 21408733 is 33780412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17825284 + 3583449 = 4222^2 + 1893^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21408733 is a prime.

It is a plaindrome in base 16.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21408703) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10704366 + 10704367.

It is an arithmetic number, because the mean of its divisors is an integer number (10704367).

Almost surely, 2^21408733 is an apocalyptic number.

It is an amenable number.

21408733 is a deficient number, since it is larger than the sum of its proper divisors (1).

21408733 is an equidigital number, since it uses as much as digits as its factorization.

21408733 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4032, while the sum is 28.

The square root of 21408733 is about 4626.9572074961. The cubic root of 21408733 is about 277.6708706055.

The spelling of 21408733 in words is "twenty-one million, four hundred eight thousand, seven hundred thirty-three".