21987330 has 16 divisors (see below), whose sum is σ = 52769664. Its totient is φ = 5863280.

The previous prime is 21987299. The next prime is 21987331. The reversal of 21987330 is 3378912.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21987291 and 21987300.

It is not an unprimeable number, because it can be changed into a prime (21987331) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 366426 + ... + 366485.

It is an arithmetic number, because the mean of its divisors is an integer number (3298104).

Almost surely, 2^21987330 is an apocalyptic number.

21987330 is an abundant number, since it is smaller than the sum of its proper divisors (30782334).

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

21987330 is a wasteful number, since it uses less digits than its factorization.

21987330 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 732921.

The product of its (nonzero) digits is 9072, while the sum is 33.

The square root of 21987330 is about 4689.0649387698. The cubic root of 21987330 is about 280.1501320719.

The spelling of 21987330 in words is "twenty-one million, nine hundred eighty-seven thousand, three hundred thirty".