1216265691 has 12 divisors (see below), whose sum is σ = 1695263528. Its totient is φ = 775588704.

The previous prime is 1216265657. The next prime is 1216265711. The reversal of 1216265691 is 1965626121.

It is not a de Polignac number, because 1216265691 - 2⁹ = 1216265179 is a prime.

It is a super-2 number, since 2×1216265691² = 2958604462207414962, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1216260691) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 381610 + ... + 384783.

Almost surely, 2^1216265691 is an apocalyptic number.

1216265691 is a deficient number, since it is larger than the sum of its proper divisors (478997837).

1216265691 is an equidigital number, since it uses as much as digits as its factorization.

1216265691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 766442 (or 766419 counting only the distinct ones).

The product of its digits is 38880, while the sum is 39.

The square root of 1216265691 is about 34875.0009462365. Note that the first 3 decimals coincide. The cubic root of 1216265691 is about 1067.4383917994.

The spelling of 1216265691 in words is "one billion, two hundred sixteen million, two hundred sixty-five thousand, six hundred ninety-one".