21778040 has 16 divisors (see below), whose sum is σ = 49000680. Its totient is φ = 8711200.

The previous prime is 21778039. The next prime is 21778049. The reversal of 21778040 is 4087712.

It is a junction number, because it is equal to n+sod(n) for n = 21777994 and 21778012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21778049) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 272186 + ... + 272265.

Almost surely, 2^21778040 is an apocalyptic number.

21778040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21778040 is an abundant number, since it is smaller than the sum of its proper divisors (27222640).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21778040 is a wasteful number, since it uses less digits than its factorization.

21778040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 544462 (or 544458 counting only the distinct ones).

The product of its (nonzero) digits is 3136, while the sum is 29.

The square root of 21778040 is about 4666.6947618202. The cubic root of 21778040 is about 279.2584117654.

The spelling of 21778040 in words is "twenty-one million, seven hundred seventy-eight thousand, forty".