7780121820 has 96 divisors (see below), whose sum is σ = 24258104640. Its totient is φ = 2070132480.

The previous prime is 7780121779. The next prime is 7780121837. The reversal of 7780121820 is 281210877.

It is a happy number.

It is a super-2 number, since 2×7780121820² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 233314 + ... + 264566.

It is an arithmetic number, because the mean of its divisors is an integer number (252688590).

Almost surely, 2^7780121820 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 7780121820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (12129052320).

7780121820 is an abundant number, since it is smaller than the sum of its proper divisors (16477982820).

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

7780121820 is a wasteful number, since it uses less digits than its factorization.

7780121820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31732 (or 31724 counting only the distinct ones).

The product of its (nonzero) digits is 12544, while the sum is 36.

The square root of 7780121820 is about 88204.9988379343. The cubic root of 7780121820 is about 1981.5063376532.

It can be divided in two parts, 7780 and 121820, that added together give a square (129600 = 360²).

The spelling of 7780121820 in words is "seven billion, seven hundred eighty million, one hundred twenty-one thousand, eight hundred twenty".