21871616 has 88 divisors (see below), whose sum is σ = 49521024. Its totient is φ = 9584640.

The previous prime is 21871609. The next prime is 21871631. The reversal of 21871616 is 61617812.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 412646 + ... + 412698.

Almost surely, 2^21871616 is an apocalyptic number.

21871616 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21871616, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24760512).

21871616 is an abundant number, since it is smaller than the sum of its proper divisors (27649408).

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

21871616 is a wasteful number, since it uses less digits than its factorization.

21871616 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 117 (or 99 counting only the distinct ones).

The product of its digits is 4032, while the sum is 32.

The square root of 21871616 is about 4676.7099546583. The cubic root of 21871616 is about 279.6578132780.

The spelling of 21871616 in words is "twenty-one million, eight hundred seventy-one thousand, six hundred sixteen".