77121990 has 128 divisors (see below), whose sum is σ = 234316800. Its totient is φ = 17867520.

The previous prime is 77121959. The next prime is 77121997. The reversal of 77121990 is 9912177.

77121990 is a nontrivial binomial coefficient, being equal to C(12420, 2).

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (77121997) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 67746 + ... + 68874.

It is an arithmetic number, because the mean of its divisors is an integer number (1830600).

Almost surely, 2^77121990 is an apocalyptic number.

77121990 is the 12419-th triangular number and also the 6210-th hexagonal number.

It is a practical number, because each smaller number is the sum of distinct divisors of 77121990, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (117158400).

77121990 is an abundant number, since it is smaller than the sum of its proper divisors (157194810).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

77121990 is a wasteful number, since it uses less digits than its factorization.

77121990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1179 (or 1173 counting only the distinct ones).

The product of its (nonzero) digits is 7938, while the sum is 36.

The square root of 77121990 is about 8781.9126618294. The cubic root of 77121990 is about 425.6566366284.

The spelling of 77121990 in words is "seventy-seven million, one hundred twenty-one thousand, nine hundred ninety".