85978721 has 2 divisors, whose sum is σ = 85978722. Its totient is φ = 85978720.

The previous prime is 85978709. The next prime is 85978723. The reversal of 85978721 is 12787958.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 83466496 + 2512225 = 9136^2 + 1585^2 .

It is a cyclic number.

It is not a de Polignac number, because 85978721 - 2¹⁸ = 85716577 is a prime.

Together with 85978723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (85978723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 42989360 + 42989361.

It is an arithmetic number, because the mean of its divisors is an integer number (42989361).

Almost surely, 2^85978721 is an apocalyptic number.

It is an amenable number.

85978721 is a deficient number, since it is larger than the sum of its proper divisors (1).

85978721 is an equidigital number, since it uses as much as digits as its factorization.

85978721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 282240, while the sum is 47.

The square root of 85978721 is about 9272.4711377281. The cubic root of 85978721 is about 441.3640879654.

The spelling of 85978721 in words is "eighty-five million, nine hundred seventy-eight thousand, seven hundred twenty-one".