21681469 has 2 divisors, whose sum is σ = 21681470. Its totient is φ = 21681468.

The previous prime is 21681467. The next prime is 21681481. The reversal of 21681469 is 96418612.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19316025 + 2365444 = 4395^2 + 1538^2 .

It is a cyclic number.

It is not a de Polignac number, because 21681469 - 2¹ = 21681467 is a prime.

It is a super-2 number, since 2×21681469² = 940172195995922, which contains 22 as substring.

Together with 21681467, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21681467) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10840734 + 10840735.

It is an arithmetic number, because the mean of its divisors is an integer number (10840735).

Almost surely, 2^21681469 is an apocalyptic number.

It is an amenable number.

21681469 is a deficient number, since it is larger than the sum of its proper divisors (1).

21681469 is an equidigital number, since it uses as much as digits as its factorization.

21681469 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20736, while the sum is 37.

The square root of 21681469 is about 4656.3364354393. The cubic root of 21681469 is about 278.8450255496.

The spelling of 21681469 in words is "twenty-one million, six hundred eighty-one thousand, four hundred sixty-nine".