21517669 has 2 divisors, whose sum is σ = 21517670. Its totient is φ = 21517668.

The previous prime is 21517649. The next prime is 21517679. The reversal of 21517669 is 96671512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13032100 + 8485569 = 3610^2 + 2913^2 .

It is a cyclic number.

It is not a de Polignac number, because 21517669 - 2⁷ = 21517541 is a prime.

It is a super-2 number, since 2×21517669² = 926020158387122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21517649) 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, 10758834 + 10758835.

It is an arithmetic number, because the mean of its divisors is an integer number (10758835).

Almost surely, 2^21517669 is an apocalyptic number.

It is an amenable number.

21517669 is a deficient number, since it is larger than the sum of its proper divisors (1).

21517669 is an equidigital number, since it uses as much as digits as its factorization.

21517669 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 22680, while the sum is 37.

The square root of 21517669 is about 4638.7141537284. The cubic root of 21517669 is about 278.1410400041.

It can be divided in two parts, 2151766 and 9, that added together give a triangular number (2151775 = T₂₀₇₄).

The spelling of 21517669 in words is "twenty-one million, five hundred seventeen thousand, six hundred sixty-nine".