1261636551 has 24 divisors (see below), whose sum is σ = 2103333024. Its totient is φ = 713793600.

The previous prime is 1261636547. The next prime is 1261636567. The reversal of 1261636551 is 1556361621.

1261636551 is a `hidden beast` number, since 1 + 2 + 616 + 36 + 5 + 5 + 1 = 666.

It is not a de Polignac number, because 1261636551 - 2² = 1261636547 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261636451) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 92776 + ... + 105501.

It is an arithmetic number, because the mean of its divisors is an integer number (87638876).

Almost surely, 2^1261636551 is an apocalyptic number.

1261636551 is a deficient number, since it is larger than the sum of its proper divisors (841696473).

1261636551 is a wasteful number, since it uses less digits than its factorization.

1261636551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 198391 (or 198388 counting only the distinct ones).

The product of its digits is 32400, while the sum is 36.

The square root of 1261636551 is about 35519.5235187636. The cubic root of 1261636551 is about 1080.5497175755.

The spelling of 1261636551 in words is "one billion, two hundred sixty-one million, six hundred thirty-six thousand, five hundred fifty-one".