1261681890 has 192 divisors, whose sum is σ = 3742848000. Its totient is φ = 270635904.

The previous prime is 1261681879. The next prime is 1261681913. The reversal of 1261681890 is 981861621.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 5557957 + ... + 5558183.

It is an arithmetic number, because the mean of its divisors is an integer number (19494000).

Almost surely, 2^1261681890 is an apocalyptic number.

1261681890 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 1261681890, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1871424000).

1261681890 is an abundant number, since it is smaller than the sum of its proper divisors (2481166110).

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

1261681890 is a wasteful number, since it uses less digits than its factorization.

1261681890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 469 (or 462 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 42.

The square root of 1261681890 is about 35520.1617394966. The cubic root of 1261681890 is about 1080.5626612020.

The spelling of 1261681890 in words is "one billion, two hundred sixty-one million, six hundred eighty-one thousand, eight hundred ninety".