77021909 has 4 divisors (see below), whose sum is σ = 77193900. Its totient is φ = 76849920.

The previous prime is 77021899. The next prime is 77021911. The reversal of 77021909 is 90912077.

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 31080625 + 45941284 = 5575^2 + 6778^2 .

It is a cyclic number.

It is not a de Polignac number, because 77021909 - 2¹² = 77017813 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (77021939) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 85322 + ... + 86219.

It is an arithmetic number, because the mean of its divisors is an integer number (19298475).

Almost surely, 2^77021909 is an apocalyptic number.

It is an amenable number.

77021909 is a deficient number, since it is larger than the sum of its proper divisors (171991).

77021909 is a wasteful number, since it uses less digits than its factorization.

77021909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 171990.

The product of its (nonzero) digits is 7938, while the sum is 35.

The square root of 77021909 is about 8776.2126797383. The cubic root of 77021909 is about 425.4724324323.

The spelling of 77021909 in words is "seventy-seven million, twenty-one thousand, nine hundred nine".