85217721 has 16 divisors (see below), whose sum is σ = 118879488. Its totient is φ = 54243200.

The previous prime is 85217711. The next prime is 85217731. The reversal of 85217721 is 12771258.

It is an interprime number because it is at equal distance from previous prime (85217711) and next prime (85217731).

It is a cyclic number.

It is not a de Polignac number, because 85217721 - 2¹³ = 85209529 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (85217711) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1590 + ... + 13151.

It is an arithmetic number, because the mean of its divisors is an integer number (7429968).

Almost surely, 2^85217721 is an apocalyptic number.

It is an amenable number.

85217721 is a deficient number, since it is larger than the sum of its proper divisors (33661767).

85217721 is a wasteful number, since it uses less digits than its factorization.

85217721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14832.

The product of its digits is 7840, while the sum is 33.

The square root of 85217721 is about 9231.3444849599. The cubic root of 85217721 is about 440.0580519135.

Adding to 85217721 its reverse (12771258), we get a palindrome (97988979).

The spelling of 85217721 in words is "eighty-five million, two hundred seventeen thousand, seven hundred twenty-one".