21778371 has 6 divisors (see below), whose sum is σ = 31457660. Its totient is φ = 14518908.

The previous prime is 21778369. The next prime is 21778387. The reversal of 21778371 is 17387712.

It is a happy number.

21778371 is a `hidden beast` number, since 217 + 78 + 371 = 666.

It is not a de Polignac number, because 21778371 - 2¹ = 21778369 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21778301) 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 in 5 ways as a sum of consecutive naturals, for example, 1209901 + ... + 1209918.

Almost surely, 2^21778371 is an apocalyptic number.

21778371 is a deficient number, since it is larger than the sum of its proper divisors (9679289).

21778371 is a wasteful number, since it uses less digits than its factorization.

21778371 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2419825 (or 2419822 counting only the distinct ones).

The product of its digits is 16464, while the sum is 36.

The square root of 21778371 is about 4666.7302257576. The cubic root of 21778371 is about 279.2598265555.

The spelling of 21778371 in words is "twenty-one million, seven hundred seventy-eight thousand, three hundred seventy-one".