28921861 has 2 divisors, whose sum is σ = 28921862. Its totient is φ = 28921860.

The previous prime is 28921831. The next prime is 28921877. The reversal of 28921861 is 16812982.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 28569025 + 352836 = 5345^2 + 594^2 .

It is a cyclic number.

It is not a de Polignac number, because 28921861 - 2⁵ = 28921829 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 28921861.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28921831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14460930 + 14460931.

It is an arithmetic number, because the mean of its divisors is an integer number (14460931).

Almost surely, 2^28921861 is an apocalyptic number.

It is an amenable number.

28921861 is a deficient number, since it is larger than the sum of its proper divisors (1).

28921861 is an equidigital number, since it uses as much as digits as its factorization.

28921861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13824, while the sum is 37.

The square root of 28921861 is about 5377.9048894528. The cubic root of 28921861 is about 306.9554944025.

It can be divided in two parts, 2892 and 1861, that added together give a triangular number (4753 = T₉₇).

The spelling of 28921861 in words is "twenty-eight million, nine hundred twenty-one thousand, eight hundred sixty-one".