21780854 has 4 divisors (see below), whose sum is σ = 32671284. Its totient is φ = 10890426.

The previous prime is 21780823. The next prime is 21780887. The reversal of 21780854 is 45808712.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5445212 + ... + 5445215.

It is an arithmetic number, because the mean of its divisors is an integer number (8167821).

Almost surely, 2^21780854 is an apocalyptic number.

21780854 is a deficient number, since it is larger than the sum of its proper divisors (10890430).

21780854 is a wasteful number, since it uses less digits than its factorization.

21780854 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10890429.

The product of its (nonzero) digits is 17920, while the sum is 35.

The square root of 21780854 is about 4666.9962502663. The cubic root of 21780854 is about 279.2704391613.

Adding to 21780854 its sum of digits (35), we get a square (21780889 = 4667²).

The spelling of 21780854 in words is "twenty-one million, seven hundred eighty thousand, eight hundred fifty-four".