1261521554 has 16 divisors (see below), whose sum is σ = 1901016000. Its totient is φ = 627856944.

The previous prime is 1261521553. The next prime is 1261521557. The reversal of 1261521554 is 4551251621.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1261521554.

It is not an unprimeable number, because it can be changed into a prime (1261521553) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 464669 + ... + 467375.

It is an arithmetic number, because the mean of its divisors is an integer number (118813500).

Almost surely, 2^1261521554 is an apocalyptic number.

1261521554 is a deficient number, since it is larger than the sum of its proper divisors (639494446).

1261521554 is a wasteful number, since it uses less digits than its factorization.

1261521554 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3697.

The product of its digits is 12000, while the sum is 32.

The square root of 1261521554 is about 35517.9046960825. The cubic root of 1261521554 is about 1080.5168862102.

The spelling of 1261521554 in words is "one billion, two hundred sixty-one million, five hundred twenty-one thousand, five hundred fifty-four".