21667771 has 16 divisors (see below), whose sum is σ = 24019200. Its totient is φ = 19454688.

The previous prime is 21667769. The next prime is 21667777. The reversal of 21667771 is 17776612.

It is not a de Polignac number, because 21667771 - 2¹ = 21667769 is a prime.

It is a super-4 number, since 4×21667771⁴ (a number of 30 digits) contains 4444 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21667771.

It is not an unprimeable number, because it can be changed into a prime (21667777) 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, 78085 + ... + 78361.

It is an arithmetic number, because the mean of its divisors is an integer number (1501200).

Almost surely, 2^21667771 is an apocalyptic number.

21667771 is a deficient number, since it is larger than the sum of its proper divisors (2351429).

21667771 is a wasteful number, since it uses less digits than its factorization.

21667771 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 498.

The product of its digits is 24696, while the sum is 37.

The square root of 21667771 is about 4654.8653041737. The cubic root of 21667771 is about 278.7862899256.

The spelling of 21667771 in words is "twenty-one million, six hundred sixty-seven thousand, seven hundred seventy-one".