1261990191 has 96 divisors (see below), whose sum is σ = 2246078464. Its totient is φ = 615859200.

The previous prime is 1261990153. The next prime is 1261990199. The reversal of 1261990191 is 1910991621.

It is not a de Polignac number, because 1261990191 - 2⁷ = 1261990063 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261990199) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 2914311 + ... + 2914743.

Almost surely, 2^1261990191 is an apocalyptic number.

1261990191 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1261990191 is a deficient number, since it is larger than the sum of its proper divisors (984088273).

1261990191 is a wasteful number, since it uses less digits than its factorization.

1261990191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 533 (or 522 counting only the distinct ones).

The product of its (nonzero) digits is 8748, while the sum is 39.

The square root of 1261990191 is about 35524.5012772875. The cubic root of 1261990191 is about 1080.6506684407.

The spelling of 1261990191 in words is "one billion, two hundred sixty-one million, nine hundred ninety thousand, one hundred ninety-one".