77261220 has 216 divisors, whose sum is σ = 262112760. Its totient is φ = 18385920.

The previous prime is 77261213. The next prime is 77261293. The reversal of 77261220 is 2216277.

It can be written as a sum of positive squares in 4 ways, for example, as 207936 + 77053284 = 456^2 + 8778^2 .

It is a super-2 number, since 2×77261220² = 11938592231776800, which contains 22 as substring.

It is an unprimeable number.

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 71 ways as a sum of consecutive naturals, for example, 1884400 + ... + 1884440.

It is an arithmetic number, because the mean of its divisors is an integer number (1213485).

Almost surely, 2^77261220 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 77261220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (131056380).

77261220 is an abundant number, since it is smaller than the sum of its proper divisors (184851540).

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

77261220 is a wasteful number, since it uses less digits than its factorization.

77261220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 123 (or 99 counting only the distinct ones).

The product of its (nonzero) digits is 2352, while the sum is 27.

The square root of 77261220 is about 8789.8361759478. The cubic root of 77261220 is about 425.9126316894.

Adding to 77261220 its reverse (2216277), we get a palindrome (79477497).

The spelling of 77261220 in words is "seventy-seven million, two hundred sixty-one thousand, two hundred twenty".