21727220 has 12 divisors (see below), whose sum is σ = 45627204. Its totient is φ = 8690880.

The previous prime is 21727217. The next prime is 21727231. The reversal of 21727220 is 2272712.

It can be written as a sum of positive squares in 2 ways, for example, as 16176484 + 5550736 = 4022^2 + 2356^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 543161 + ... + 543200.

It is an arithmetic number, because the mean of its divisors is an integer number (3802267).

Almost surely, 2^21727220 is an apocalyptic number.

21727220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21727220 is an abundant number, since it is smaller than the sum of its proper divisors (23899984).

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

21727220 is a wasteful number, since it uses less digits than its factorization.

21727220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1086370 (or 1086368 counting only the distinct ones).

The product of its (nonzero) digits is 784, while the sum is 23.

The square root of 21727220 is about 4661.2466143726. The cubic root of 21727220 is about 279.0410220467.

Adding to 21727220 its reverse (2272712), we get a palindrome (23999932).

The spelling of 21727220 in words is "twenty-one million, seven hundred twenty-seven thousand, two hundred twenty".