21032730 has 32 divisors (see below), whose sum is σ = 56088000. Its totient is φ = 5608656.

The previous prime is 21032699. The next prime is 21032731. The reversal of 21032730 is 3723012.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21032731) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 38680 + ... + 39219.

It is an arithmetic number, because the mean of its divisors is an integer number (1752750).

Almost surely, 2^21032730 is an apocalyptic number.

21032730 is an abundant number, since it is smaller than the sum of its proper divisors (35055270).

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

21032730 is a wasteful number, since it uses less digits than its factorization.

21032730 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77915 (or 77909 counting only the distinct ones).

The product of its (nonzero) digits is 252, while the sum is 18.

The square root of 21032730 is about 4586.1454403453. The cubic root of 21032730 is about 276.0356759176.

Adding to 21032730 its reverse (3723012), we get a palindrome (24755742).

The spelling of 21032730 in words is "twenty-one million, thirty-two thousand, seven hundred thirty".