1261965921 has 16 divisors (see below), whose sum is σ = 1787438400. Its totient is φ = 789715008.

The previous prime is 1261965917. The next prime is 1261965953. The reversal of 1261965921 is 1295691621.

It is not a de Polignac number, because 1261965921 - 2² = 1261965917 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1261965961) 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, 95346 + ... + 107771.

It is an arithmetic number, because the mean of its divisors is an integer number (111714900).

Almost surely, 2^1261965921 is an apocalyptic number.

It is an amenable number.

1261965921 is a deficient number, since it is larger than the sum of its proper divisors (525472479).

1261965921 is a wasteful number, since it uses less digits than its factorization.

1261965921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 203248.

The product of its digits is 58320, while the sum is 42.

The square root of 1261965921 is about 35524.1596804203. The cubic root of 1261965921 is about 1080.6437408750.

The spelling of 1261965921 in words is "one billion, two hundred sixty-one million, nine hundred sixty-five thousand, nine hundred twenty-one".