21061320 has 64 divisors (see below), whose sum is σ = 72213120. Its totient is φ = 4813824.

The previous prime is 21061309. The next prime is 21061343. The reversal of 21061320 is 2316012.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21061320.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 11697 + ... + 13376.

It is an arithmetic number, because the mean of its divisors is an integer number (1128330).

Almost surely, 2^21061320 is an apocalyptic number.

21061320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21061320 is an abundant number, since it is smaller than the sum of its proper divisors (51151800).

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

21061320 is a wasteful number, since it uses less digits than its factorization.

21061320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25094 (or 25090 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 15.

The square root of 21061320 is about 4589.2613784791. The cubic root of 21061320 is about 276.1606919735.

Adding to 21061320 its reverse (2316012), we get a palindrome (23377332).

The spelling of 21061320 in words is "twenty-one million, sixty-one thousand, three hundred twenty".