1977661440 has 384 divisors, whose sum is σ = 7359206400. Its totient is φ = 502824960.

The previous prime is 1977661429. The next prime is 1977661453. The reversal of 1977661440 is 441667791.

It is a tau number, because it is divible by the number of its divisors (384).

It is a super-2 number, since 2×1977661440² = 7822289542525747200, which contains 22 as substring.

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

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, 6358885 + ... + 6359195.

It is an arithmetic number, because the mean of its divisors is an integer number (19164600).

Almost surely, 2^1977661440 is an apocalyptic number.

1977661440 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1977661440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3679603200).

1977661440 is an abundant number, since it is smaller than the sum of its proper divisors (5381544960).

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

1977661440 is a wasteful number, since it uses less digits than its factorization.

1977661440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 370 (or 344 counting only the distinct ones).

The product of its (nonzero) digits is 254016, while the sum is 45.

The square root of 1977661440 is about 44470.9055450864. The cubic root of 1977661440 is about 1255.2126727513.

The spelling of 1977661440 in words is "one billion, nine hundred seventy-seven million, six hundred sixty-one thousand, four hundred forty".