21677720 has 64 divisors (see below), whose sum is σ = 52488000. Its totient is φ = 8028160.

The previous prime is 21677717. The next prime is 21677723. The reversal of 21677720 is 2777612.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21677717) and next prime (21677723).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21677723) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 48056 + ... + 48504.

It is an arithmetic number, because the mean of its divisors is an integer number (820125).

Almost surely, 2^21677720 is an apocalyptic number.

21677720 is a gapful number since it is divisible by the number (20) 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 21677720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26244000).

21677720 is an abundant number, since it is smaller than the sum of its proper divisors (30810280).

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

21677720 is a wasteful number, since it uses less digits than its factorization.

21677720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 548 (or 544 counting only the distinct ones).

The product of its (nonzero) digits is 8232, while the sum is 32.

The square root of 21677720 is about 4655.9338483273. The cubic root of 21677720 is about 278.8289526802.

The spelling of 21677720 in words is "twenty-one million, six hundred seventy-seven thousand, seven hundred twenty".