21920278 has 4 divisors (see below), whose sum is σ = 32880420. Its totient is φ = 10960138.

The previous prime is 21920263. The next prime is 21920279. The reversal of 21920278 is 87202912.

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

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21920279) by changing a digit.

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, 5480068 + ... + 5480071.

It is an arithmetic number, because the mean of its divisors is an integer number (8220105).

Almost surely, 2^21920278 is an apocalyptic number.

21920278 is a deficient number, since it is larger than the sum of its proper divisors (10960142).

21920278 is a wasteful number, since it uses less digits than its factorization.

21920278 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10960141.

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 21920278 is about 4681.9096531223. The cubic root of 21920278 is about 279.8650625325.

The spelling of 21920278 in words is "twenty-one million, nine hundred twenty thousand, two hundred seventy-eight".