821521973 has 2 divisors, whose sum is σ = 821521974. Its totient is φ = 821521972.

The previous prime is 821521951. The next prime is 821521999. The reversal of 821521973 is 379125128.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 568011889 + 253510084 = 23833^2 + 15922^2 .

It is a cyclic number.

It is not a de Polignac number, because 821521973 - 2¹⁰ = 821520949 is a prime.

It is a super-3 number, since 3×821521973³ (a number of 28 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (821521903) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410760986 + 410760987.

It is an arithmetic number, because the mean of its divisors is an integer number (410760987).

Almost surely, 2^821521973 is an apocalyptic number.

It is an amenable number.

821521973 is a deficient number, since it is larger than the sum of its proper divisors (1).

821521973 is an equidigital number, since it uses as much as digits as its factorization.

821521973 is an evil number, because the sum of its binary digits is even.

The product of its digits is 30240, while the sum is 38.

The square root of 821521973 is about 28662.2046081595. The cubic root of 821521973 is about 936.5688904888.

The spelling of 821521973 in words is "eight hundred twenty-one million, five hundred twenty-one thousand, nine hundred seventy-three".