821157493 has 4 divisors (see below), whose sum is σ = 884323468. Its totient is φ = 757991520.

The previous prime is 821157487. The next prime is 821157517. The reversal of 821157493 is 394751128.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 425266884 + 395890609 = 20622^2 + 19897^2 .

It is not a de Polignac number, because 821157493 - 2²⁹ = 284286581 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 (821157413) 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, 31582968 + ... + 31582993.

It is an arithmetic number, because the mean of its divisors is an integer number (221080867).

Almost surely, 2^821157493 is an apocalyptic number.

It is an amenable number.

821157493 is a deficient number, since it is larger than the sum of its proper divisors (63165975).

821157493 is a wasteful number, since it uses less digits than its factorization.

821157493 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63165974.

The product of its digits is 60480, while the sum is 40.

The square root of 821157493 is about 28655.8457038001. The cubic root of 821157493 is about 936.4303625954.

The spelling of 821157493 in words is "eight hundred twenty-one million, one hundred fifty-seven thousand, four hundred ninety-three".