27820721 has 4 divisors (see below), whose sum is σ = 29457252. Its totient is φ = 26184192.

The previous prime is 27820691. The next prime is 27820729. The reversal of 27820721 is 12702872.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 14167696 + 13653025 = 3764^2 + 3695^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-27820721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (27820729) 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, 818240 + ... + 818273.

It is an arithmetic number, because the mean of its divisors is an integer number (7364313).

Almost surely, 2^27820721 is an apocalyptic number.

It is an amenable number.

27820721 is a deficient number, since it is larger than the sum of its proper divisors (1636531).

27820721 is a wasteful number, since it uses less digits than its factorization.

27820721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1636530.

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

The square root of 27820721 is about 5274.5351453943. The cubic root of 27820721 is about 303.0094178108.

The spelling of 27820721 in words is "twenty-seven million, eight hundred twenty thousand, seven hundred twenty-one".