21509770 has 8 divisors (see below), whose sum is σ = 38717604. Its totient is φ = 8603904.

The previous prime is 21509737. The next prime is 21509771. The reversal of 21509770 is 7790512.

It can be written as a sum of positive squares in 2 ways, for example, as 21372129 + 137641 = 4623^2 + 371^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21509771) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1075479 + ... + 1075498.

Almost surely, 2^21509770 is an apocalyptic number.

21509770 is a deficient number, since it is larger than the sum of its proper divisors (17207834).

21509770 is a wasteful number, since it uses less digits than its factorization.

21509770 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2150984.

The product of its (nonzero) digits is 4410, while the sum is 31.

The square root of 21509770 is about 4637.8626542838. The cubic root of 21509770 is about 278.1070012339.

The spelling of 21509770 in words is "twenty-one million, five hundred nine thousand, seven hundred seventy".