27971821 has 2 divisors, whose sum is σ = 27971822. Its totient is φ = 27971820.

The previous prime is 27971809. The next prime is 27971837. The reversal of 27971821 is 12817972.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 26409321 + 1562500 = 5139^2 + 1250^2 .

It is a cyclic number.

It is not a de Polignac number, because 27971821 - 2⁵ = 27971789 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (27971861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 13985910 + 13985911.

It is an arithmetic number, because the mean of its divisors is an integer number (13985911).

Almost surely, 2^27971821 is an apocalyptic number.

It is an amenable number.

27971821 is a deficient number, since it is larger than the sum of its proper divisors (1).

27971821 is an equidigital number, since it uses as much as digits as its factorization.

27971821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 14112, while the sum is 37.

The square root of 27971821 is about 5288.8392866488. The cubic root of 27971821 is about 303.5569962808.

The spelling of 27971821 in words is "twenty-seven million, nine hundred seventy-one thousand, eight hundred twenty-one".