21077784 has 96 divisors (see below), whose sum is σ = 70281120. Its totient is φ = 5557248.

The previous prime is 21077779. The next prime is 21077803. The reversal of 21077784 is 48777012.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4944 + ... + 8160.

It is an arithmetic number, because the mean of its divisors is an integer number (732095).

Almost surely, 2^21077784 is an apocalyptic number.

21077784 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21077784, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35140560).

21077784 is an abundant number, since it is smaller than the sum of its proper divisors (49203336).

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

21077784 is a wasteful number, since it uses less digits than its factorization.

21077784 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3249 (or 3242 counting only the distinct ones).

The product of its (nonzero) digits is 21952, while the sum is 36.

The square root of 21077784 is about 4591.0547807666. The cubic root of 21077784 is about 276.2326331022.

The spelling of 21077784 in words is "twenty-one million, seventy-seven thousand, seven hundred eighty-four".