21993888 has 96 divisors (see below), whose sum is σ = 68898816. Its totient is φ = 6006528.

The previous prime is 21993871. The next prime is 21993893. The reversal of 21993888 is 88839912.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (96).

It is a super-2 number, since 2×21993888² = 967462218713088, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (48).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14745 + ... + 16167.

It is an arithmetic number, because the mean of its divisors is an integer number (717696).

Almost surely, 2^21993888 is an apocalyptic number.

21993888 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 21993888, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34449408).

21993888 is an abundant number, since it is smaller than the sum of its proper divisors (46904928).

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

21993888 is a wasteful number, since it uses less digits than its factorization.

21993888 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1466 (or 1458 counting only the distinct ones).

The product of its digits is 248832, while the sum is 48.

The square root of 21993888 is about 4689.7641731754. The cubic root of 21993888 is about 280.1779820798.

The spelling of 21993888 in words is "twenty-one million, nine hundred ninety-three thousand, eight hundred eighty-eight".