85721021 has 4 divisors (see below), whose sum is σ = 90763452. Its totient is φ = 80678592.

The previous prime is 85720993. The next prime is 85721047. The reversal of 85721021 is 12012758.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12012758 = 2 ⋅6006379.

It can be written as a sum of positive squares in 2 ways, for example, as 32649796 + 53071225 = 5714^2 + 7285^2 .

It is a cyclic number.

It is not a de Polignac number, because 85721021 - 2²⁶ = 18612157 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (85721081) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2521190 + ... + 2521223.

It is an arithmetic number, because the mean of its divisors is an integer number (22690863).

Almost surely, 2^85721021 is an apocalyptic number.

It is an amenable number.

85721021 is a deficient number, since it is larger than the sum of its proper divisors (5042431).

85721021 is a wasteful number, since it uses less digits than its factorization.

85721021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5042430.

The product of its (nonzero) digits is 1120, while the sum is 26.

The square root of 85721021 is about 9258.5647375822. The cubic root of 85721021 is about 440.9226866934.

Adding to 85721021 its reverse (12012758), we get a palindrome (97733779).

The spelling of 85721021 in words is "eighty-five million, seven hundred twenty-one thousand, twenty-one".