21891771 has 24 divisors (see below), whose sum is σ = 34645104. Its totient is φ = 13210560.

The previous prime is 21891761. The next prime is 21891787. The reversal of 21891771 is 17719812.

It is not a de Polignac number, because 21891771 - 2¹⁴ = 21875387 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21891761) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 39025 + ... + 39581.

It is an arithmetic number, because the mean of its divisors is an integer number (1443546).

Almost surely, 2^21891771 is an apocalyptic number.

21891771 is a deficient number, since it is larger than the sum of its proper divisors (12753333).

21891771 is a wasteful number, since it uses less digits than its factorization.

21891771 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 971 (or 968 counting only the distinct ones).

The product of its digits is 7056, while the sum is 36.

The square root of 21891771 is about 4678.8642852727. The cubic root of 21891771 is about 279.7436897665.

The spelling of 21891771 in words is "twenty-one million, eight hundred ninety-one thousand, seven hundred seventy-one".