1261355621 has 16 divisors (see below), whose sum is σ = 1328629248. Its totient is φ = 1195905600.

The previous prime is 1261355617. The next prime is 1261355651. The reversal of 1261355621 is 1265531621.

It is not a de Polignac number, because 1261355621 - 2² = 1261355617 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261355651) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 533975 + ... + 536331.

It is an arithmetic number, because the mean of its divisors is an integer number (83039328).

Almost surely, 2^1261355621 is an apocalyptic number.

It is an amenable number.

1261355621 is a deficient number, since it is larger than the sum of its proper divisors (67273627).

1261355621 is a wasteful number, since it uses less digits than its factorization.

1261355621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2732.

The product of its digits is 10800, while the sum is 32.

The square root of 1261355621 is about 35515.5687128898. The cubic root of 1261355621 is about 1080.4695092234.

The spelling of 1261355621 in words is "one billion, two hundred sixty-one million, three hundred fifty-five thousand, six hundred twenty-one".