21871311 has 32 divisors (see below), whose sum is σ = 36883968. Its totient is φ = 11197440.

The previous prime is 21871303. The next prime is 21871319. The reversal of 21871311 is 11317812.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21871303) and next prime (21871319).

It is not a de Polignac number, because 21871311 - 2³ = 21871303 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21871319) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 16215 + ... + 17511.

It is an arithmetic number, because the mean of its divisors is an integer number (1152624).

Almost surely, 2^21871311 is an apocalyptic number.

21871311 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21871311 is a deficient number, since it is larger than the sum of its proper divisors (15012657).

21871311 is a wasteful number, since it uses less digits than its factorization.

21871311 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1391.

The product of its digits is 336, while the sum is 24.

The square root of 21871311 is about 4676.6773461508. The cubic root of 21871311 is about 279.6565133279.

The spelling of 21871311 in words is "twenty-one million, eight hundred seventy-one thousand, three hundred eleven".