71390821 has 4 divisors (see below), whose sum is σ = 71455852. Its totient is φ = 71325792.

The previous prime is 71390807. The next prime is 71390831. The reversal of 71390821 is 12809317.

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 18610596 + 52780225 = 4314^2 + 7265^2 .

It is a cyclic number.

It is not a de Polignac number, because 71390821 - 2¹¹ = 71388773 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 (71390831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 30840 + ... + 33073.

It is an arithmetic number, because the mean of its divisors is an integer number (17863963).

Almost surely, 2^71390821 is an apocalyptic number.

It is an amenable number.

71390821 is a deficient number, since it is larger than the sum of its proper divisors (65031).

71390821 is a wasteful number, since it uses less digits than its factorization.

71390821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 65030.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 71390821 is about 8449.3089066503. The cubic root of 71390821 is about 414.8401590854.

The spelling of 71390821 in words is "seventy-one million, three hundred ninety thousand, eight hundred twenty-one".