77665921 has 2 divisors, whose sum is σ = 77665922. Its totient is φ = 77665920.

The previous prime is 77665909. The next prime is 77665933. The reversal of 77665921 is 12956677.

It is a balanced prime because it is at equal distance from previous prime (77665909) and next prime (77665933).

It can be written as a sum of positive squares in only one way, i.e., 63377521 + 14288400 = 7961^2 + 3780^2 .

It is a cyclic number.

It is not a de Polignac number, because 77665921 - 2²¹ = 75568769 is a prime.

It is not a weakly prime, because it can be changed into another prime (77665981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38832960 + 38832961.

It is an arithmetic number, because the mean of its divisors is an integer number (38832961).

Almost surely, 2^77665921 is an apocalyptic number.

It is an amenable number.

77665921 is a deficient number, since it is larger than the sum of its proper divisors (1).

77665921 is an equidigital number, since it uses as much as digits as its factorization.

77665921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 158760, while the sum is 43.

The square root of 77665921 is about 8812.8270719446. The cubic root of 77665921 is about 426.6549928311.

The spelling of 77665921 in words is "seventy-seven million, six hundred sixty-five thousand, nine hundred twenty-one".