21133720 has 32 divisors (see below), whose sum is σ = 50349600. Its totient is φ = 7955968.

The previous prime is 21133687. The next prime is 21133727. The reversal of 21133720 is 2733112.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21133727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14860 + ... + 16219.

It is an arithmetic number, because the mean of its divisors is an integer number (1573425).

Almost surely, 2^21133720 is an apocalyptic number.

21133720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21133720 is an abundant number, since it is smaller than the sum of its proper divisors (29215880).

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

21133720 is a wasteful number, since it uses less digits than its factorization.

21133720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31107 (or 31103 counting only the distinct ones).

The product of its (nonzero) digits is 252, while the sum is 19.

The square root of 21133720 is about 4597.1425907840. The cubic root of 21133720 is about 276.4767716775.

Adding to 21133720 its reverse (2733112), we get a palindrome (23866832).

The spelling of 21133720 in words is "twenty-one million, one hundred thirty-three thousand, seven hundred twenty".