921491861 has 2 divisors, whose sum is σ = 921491862. Its totient is φ = 921491860.

The previous prime is 921491819. The next prime is 921491873. The reversal of 921491861 is 168194129.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 466992100 + 454499761 = 21610^2 + 21319^2 .

It is a cyclic number.

It is not a de Polignac number, because 921491861 - 2⁶ = 921491797 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (921491801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 460745930 + 460745931.

It is an arithmetic number, because the mean of its divisors is an integer number (460745931).

Almost surely, 2^921491861 is an apocalyptic number.

It is an amenable number.

921491861 is a deficient number, since it is larger than the sum of its proper divisors (1).

921491861 is an equidigital number, since it uses as much as digits as its factorization.

921491861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 31104, while the sum is 41.

The square root of 921491861 is about 30356.0844148253. The cubic root of 921491861 is about 973.1142551153.

The spelling of 921491861 in words is "nine hundred twenty-one million, four hundred ninety-one thousand, eight hundred sixty-one".