21681069 has 16 divisors (see below), whose sum is σ = 30735360. Its totient is φ = 13594560.

The previous prime is 21681061. The next prime is 21681091. The reversal of 21681069 is 96018612.

It is not a de Polignac number, because 21681069 - 2³ = 21681061 is a prime.

It is a super-2 number, since 2×21681069² = 940137505965522, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21681061) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14004 + ... + 15474.

It is an arithmetic number, because the mean of its divisors is an integer number (1920960).

Almost surely, 2^21681069 is an apocalyptic number.

It is an amenable number.

21681069 is a deficient number, since it is larger than the sum of its proper divisors (9054291).

21681069 is an equidigital number, since it uses as much as digits as its factorization.

21681069 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1525 (or 1491 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 33.

The square root of 21681069 is about 4656.2934830184. The cubic root of 21681069 is about 278.8433107412.

The spelling of 21681069 in words is "twenty-one million, six hundred eighty-one thousand, sixty-nine".