21011788 has 72 divisors (see below), whose sum is σ = 45964800. Its totient is φ = 8360352.

The previous prime is 21011761. The next prime is 21011789. The reversal of 21011788 is 88711012.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is not an unprimeable number, because it can be changed into a prime (21011789) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 265933 + ... + 266011.

It is an arithmetic number, because the mean of its divisors is an integer number (638400).

Almost surely, 2^21011788 is an apocalyptic number.

21011788 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 21011788, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22982400).

21011788 is an abundant number, since it is smaller than the sum of its proper divisors (24953012).

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

21011788 is a wasteful number, since it uses less digits than its factorization.

21011788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 179 (or 170 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 28.

The square root of 21011788 is about 4583.8616907581. The cubic root of 21011788 is about 275.9440305188.

The spelling of 21011788 in words is "twenty-one million, eleven thousand, seven hundred eighty-eight".