21631771 has 4 divisors (see below), whose sum is σ = 24722032. Its totient is φ = 18541512.

The previous prime is 21631739. The next prime is 21631777. The reversal of 21631771 is 17713612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21631771 - 2⁵ = 21631739 is a prime.

It is a super-3 number, since 3×21631771³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21631777) 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 in 3 ways as a sum of consecutive naturals, for example, 1545120 + ... + 1545133.

It is an arithmetic number, because the mean of its divisors is an integer number (6180508).

Almost surely, 2^21631771 is an apocalyptic number.

21631771 is a deficient number, since it is larger than the sum of its proper divisors (3090261).

21631771 is an equidigital number, since it uses as much as digits as its factorization.

21631771 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3090260.

The product of its digits is 1764, while the sum is 28.

The square root of 21631771 is about 4650.9967748860. The cubic root of 21631771 is about 278.6318074939.

The spelling of 21631771 in words is "twenty-one million, six hundred thirty-one thousand, seven hundred seventy-one".