21780158 has 4 divisors (see below), whose sum is σ = 32670240. Its totient is φ = 10890078.

The previous prime is 21780151. The next prime is 21780203. The reversal of 21780158 is 85108712.

It is a happy number.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21780151) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5445038 + ... + 5445041.

It is an arithmetic number, because the mean of its divisors is an integer number (8167560).

Almost surely, 2^21780158 is an apocalyptic number.

21780158 is a deficient number, since it is larger than the sum of its proper divisors (10890082).

21780158 is a wasteful number, since it uses less digits than its factorization.

21780158 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10890081.

The product of its (nonzero) digits is 4480, while the sum is 32.

The square root of 21780158 is about 4666.9216835083. The cubic root of 21780158 is about 279.2674644647.

The spelling of 21780158 in words is "twenty-one million, seven hundred eighty thousand, one hundred fifty-eight".