77921 has 4 divisors (see below), whose sum is σ = 79152. Its totient is φ = 76692.

The previous prime is 77899. The next prime is 77929. The reversal of 77921 is 12977.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12977 = 19 ⋅683.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-77921 is a prime.

It is a Duffinian number.

It is a plaindrome in base 9.

It is not an unprimeable number, because it can be changed into a prime (77929) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 515 + ... + 648.

It is an arithmetic number, because the mean of its divisors is an integer number (19788).

2⁷⁷⁹²¹ is an apocalyptic number.

It is an amenable number.

77921 is a deficient number, since it is larger than the sum of its proper divisors (1231).

77921 is a wasteful number, since it uses less digits than its factorization.

77921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1230.

The product of its digits is 882, while the sum is 26.

The square root of 77921 is about 279.1433323581. The cubic root of 77921 is about 42.7121571565.

The spelling of 77921 in words is "seventy-seven thousand, nine hundred twenty-one".