73781821 has 2 divisors, whose sum is σ = 73781822. Its totient is φ = 73781820.

The previous prime is 73781803. The next prime is 73781833. The reversal of 73781821 is 12818737.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 59074596 + 14707225 = 7686^2 + 3835^2 .

It is an emirp because it is prime and its reverse (12818737) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 73781821 - 2¹³ = 73773629 is a prime.

It is a super-2 number, since 2×73781821² = 10887514220152082, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (73781221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36890910 + 36890911.

It is an arithmetic number, because the mean of its divisors is an integer number (36890911).

Almost surely, 2^73781821 is an apocalyptic number.

It is an amenable number.

73781821 is a deficient number, since it is larger than the sum of its proper divisors (1).

73781821 is an equidigital number, since it uses as much as digits as its factorization.

73781821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18816, while the sum is 37.

The square root of 73781821 is about 8589.6345091046. The cubic root of 73781821 is about 419.4206316197.

The spelling of 73781821 in words is "seventy-three million, seven hundred eighty-one thousand, eight hundred twenty-one".