77921947 has 2 divisors, whose sum is σ = 77921948. Its totient is φ = 77921946.

The previous prime is 77921933. The next prime is 77921951. The reversal of 77921947 is 74912977.

It is a strong prime.

It is an emirp because it is prime and its reverse (74912977) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 77921947 - 2¹¹ = 77919899 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 77921897 and 77921906.

It is not a weakly prime, because it can be changed into another prime (77921647) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38960973 + 38960974.

It is an arithmetic number, because the mean of its divisors is an integer number (38960974).

Almost surely, 2^77921947 is an apocalyptic number.

77921947 is a deficient number, since it is larger than the sum of its proper divisors (1).

77921947 is an equidigital number, since it uses as much as digits as its factorization.

77921947 is an evil number, because the sum of its binary digits is even.

The product of its digits is 222264, while the sum is 46.

The square root of 77921947 is about 8827.3408793362. The cubic root of 77921947 is about 427.1233018749.

The spelling of 77921947 in words is "seventy-seven million, nine hundred twenty-one thousand, nine hundred forty-seven".