12561402640 has 20 divisors (see below), whose sum is σ = 29205261324. Its totient is φ = 5024561024.

The previous prime is 12561402619. The next prime is 12561402677. The reversal of 12561402640 is 4620416521.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 1271065104 + 11290337536 = 35652^2 + 106256^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 78508687 + ... + 78508846.

Almost surely, 2^12561402640 is an apocalyptic number.

12561402640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

12561402640 is an abundant number, since it is smaller than the sum of its proper divisors (16643858684).

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

12561402640 is a wasteful number, since it uses less digits than its factorization.

12561402640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 157017546 (or 157017540 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 31.

The spelling of 12561402640 in words is "twelve billion, five hundred sixty-one million, four hundred two thousand, six hundred forty".