27661921 has 20 divisors (see below), whose sum is σ = 33175044. Its totient is φ = 23049600.

The previous prime is 27661913. The next prime is 27661979. The reversal of 27661921 is 12916672.

It can be written as a sum of positive squares in 2 ways, for example, as 8643600 + 19018321 = 2940^2 + 4361^2 .

It is not a de Polignac number, because 27661921 - 2³ = 27661913 is a prime.

It is not an unprimeable number, because it can be changed into a prime (27661901) 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 19 ways as a sum of consecutive naturals, for example, 98301 + ... + 98581.

Almost surely, 2^27661921 is an apocalyptic number.

It is an amenable number.

27661921 is a deficient number, since it is larger than the sum of its proper divisors (5513123).

27661921 is an frugal number, since it uses more digits than its factorization.

27661921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 350 (or 329 counting only the distinct ones).

The product of its digits is 9072, while the sum is 34.

The square root of 27661921 is about 5259.4601433988. The cubic root of 27661921 is about 302.4317939251.

It can be divided in two parts, 27661 and 921, that added together give a palindrome (28582).

The spelling of 27661921 in words is "twenty-seven million, six hundred sixty-one thousand, nine hundred twenty-one".