21178669 has 2 divisors, whose sum is σ = 21178670. Its totient is φ = 21178668.

The previous prime is 21178649. The next prime is 21178697. The reversal of 21178669 is 96687112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20593444 + 585225 = 4538^2 + 765^2 .

It is a cyclic number.

It is not a de Polignac number, because 21178669 - 2²³ = 12790061 is a prime.

It is a super-2 number, since 2×21178669² = 897072041223122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21178609) 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, 10589334 + 10589335.

It is an arithmetic number, because the mean of its divisors is an integer number (10589335).

Almost surely, 2^21178669 is an apocalyptic number.

It is an amenable number.

21178669 is a deficient number, since it is larger than the sum of its proper divisors (1).

21178669 is an equidigital number, since it uses as much as digits as its factorization.

21178669 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 40.

The square root of 21178669 is about 4602.0287917396. The cubic root of 21178669 is about 276.6726443443.

The spelling of 21178669 in words is "twenty-one million, one hundred seventy-eight thousand, six hundred sixty-nine".