21081588 has 36 divisors (see below), whose sum is σ = 54072480. Its totient is φ = 6387920.

The previous prime is 21081569. The next prime is 21081589. The reversal of 21081588 is 88518012.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21081589) 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 11 ways as a sum of consecutive naturals, for example, 5808 + ... + 8711.

Almost surely, 2^21081588 is an apocalyptic number.

It is an amenable number.

21081588 is an abundant number, since it is smaller than the sum of its proper divisors (32990892).

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

21081588 is a wasteful number, since it uses less digits than its factorization.

21081588 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14548 (or 14535 counting only the distinct ones).

The product of its (nonzero) digits is 5120, while the sum is 33.

The square root of 21081588 is about 4591.4690459590. The cubic root of 21081588 is about 276.2492497403.

21081588 divided by its sum of digits (33) gives a palindrome (638836).

The spelling of 21081588 in words is "twenty-one million, eighty-one thousand, five hundred eighty-eight".