21871668 has 48 divisors (see below), whose sum is σ = 62814080. Its totient is φ = 5768064.

The previous prime is 21871667. The next prime is 21871721. The reversal of 21871668 is 86617812.

It is a super-2 number, since 2×21871668² = 956739722204448, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21871667) 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 15 ways as a sum of consecutive naturals, for example, 8923 + ... + 11106.

Almost surely, 2^21871668 is an apocalyptic number.

21871668 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21871668 is an abundant number, since it is smaller than the sum of its proper divisors (40942412).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21871668 is a wasteful number, since it uses less digits than its factorization.

21871668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20056 (or 20054 counting only the distinct ones).

The product of its digits is 32256, while the sum is 39.

The square root of 21871668 is about 4676.7155141189. The cubic root of 21871668 is about 279.6580349077.

The spelling of 21871668 in words is "twenty-one million, eight hundred seventy-one thousand, six hundred sixty-eight".