21788770 has 8 divisors (see below), whose sum is σ = 39219804. Its totient is φ = 8715504.

The previous prime is 21788749. The next prime is 21788771. The reversal of 21788770 is 7788712.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 20802721 + 986049 = 4561^2 + 993^2 .

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

It is a super-2 number, since 2×21788770² = 949500996225800, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21788771) 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 3 ways as a sum of consecutive naturals, for example, 1089429 + ... + 1089448.

Almost surely, 2^21788770 is an apocalyptic number.

21788770 is a deficient number, since it is larger than the sum of its proper divisors (17431034).

21788770 is a wasteful number, since it uses less digits than its factorization.

21788770 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2178884.

The product of its (nonzero) digits is 43904, while the sum is 40.

The square root of 21788770 is about 4667.8442561851. The cubic root of 21788770 is about 279.3042676028.

The spelling of 21788770 in words is "twenty-one million, seven hundred eighty-eight thousand, seven hundred seventy".