21961688 has 96 divisors (see below), whose sum is σ = 53049600. Its totient is φ = 8329728.

The previous prime is 21961627. The next prime is 21961697. The reversal of 21961688 is 88616912.

Its product of digits (41472) is a multiple of the sum of its prime divisors (108).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 372203 + ... + 372261.

It is an arithmetic number, because the mean of its divisors is an integer number (552600).

Almost surely, 2^21961688 is an apocalyptic number.

21961688 is a gapful number since it is divisible by the number (28) 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 21961688, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26524800).

21961688 is an abundant number, since it is smaller than the sum of its proper divisors (31087912).

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

21961688 is a wasteful number, since it uses less digits than its factorization.

21961688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129 (or 108 counting only the distinct ones).

The product of its digits is 41472, while the sum is 41.

The square root of 21961688 is about 4686.3299072942. The cubic root of 21961688 is about 280.0411844182.

The spelling of 21961688 in words is "twenty-one million, nine hundred sixty-one thousand, six hundred eighty-eight".