21780898 has 4 divisors (see below), whose sum is σ = 32671350. Its totient is φ = 10890448.

The previous prime is 21780887. The next prime is 21780907. The reversal of 21780898 is 89808712.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 21780889 + 9 = 4667^2 + 3^2 .

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 as a sum of consecutive naturals, namely, 5445223 + ... + 5445226.

Almost surely, 2^21780898 is an apocalyptic number.

21780898 is a deficient number, since it is larger than the sum of its proper divisors (10890452).

21780898 is a wasteful number, since it uses less digits than its factorization.

21780898 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10890451.

The product of its (nonzero) digits is 64512, while the sum is 43.

The square root of 21780898 is about 4667.0009642167. Note that the first 3 decimals coincide. The cubic root of 21780898 is about 279.2706272147.

The spelling of 21780898 in words is "twenty-one million, seven hundred eighty thousand, eight hundred ninety-eight".