21780863 has 8 divisors (see below), whose sum is σ = 23665488. Its totient is φ = 19926144.

The previous prime is 21780823. The next prime is 21780887. The reversal of 21780863 is 36808712.

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

It is a cyclic number.

It is not a de Polignac number, because 21780863 - 2¹⁶ = 21715327 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21780823) 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, 5945 + ... + 8882.

It is an arithmetic number, because the mean of its divisors is an integer number (2958186).

Almost surely, 2^21780863 is an apocalyptic number.

21780863 is a deficient number, since it is larger than the sum of its proper divisors (1884625).

21780863 is a wasteful number, since it uses less digits than its factorization.

21780863 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14953.

The product of its (nonzero) digits is 16128, while the sum is 35.

The square root of 21780863 is about 4666.9972144838. The cubic root of 21780863 is about 279.2704776268.

The spelling of 21780863 in words is "twenty-one million, seven hundred eighty thousand, eight hundred sixty-three".