77872121820 has 240 divisors, whose sum is σ = 253878831360. Its totient is φ = 19957238784.

The previous prime is 77872121783. The next prime is 77872121827. The reversal of 77872121820 is 2812127877.

It is a super-2 number, since 2×77872121820² (a number of 23 digits) contains 22 as substring.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (77872121827) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 10472824 + ... + 10480256.

It is an arithmetic number, because the mean of its divisors is an integer number (1057828464).

Almost surely, 2^77872121820 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 77872121820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (126939415680).

77872121820 is an abundant number, since it is smaller than the sum of its proper divisors (176006709540).

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

77872121820 is a wasteful number, since it uses less digits than its factorization.

77872121820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7706 (or 7695 counting only the distinct ones).

The product of its (nonzero) digits is 175616, while the sum is 45.

The spelling of 77872121820 in words is "seventy-seven billion, eight hundred seventy-two million, one hundred twenty-one thousand, eight hundred twenty".