1216611540 has 36 divisors (see below), whose sum is σ = 3690388884. Its totient is φ = 324429696.

The previous prime is 1216611499. The next prime is 1216611547. The reversal of 1216611540 is 451166121.

1216611540 is a `hidden beast` number, since 1 + 2 + 1 + 6 + 611 + 5 + 40 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 553755024 + 662856516 = 23532^2 + 25746^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-2 number, since 2×1216611540² = 2960287278522343200, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1216611547) 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, 3379297 + ... + 3379656.

Almost surely, 2^1216611540 is an apocalyptic number.

1216611540 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1216611540 is an abundant number, since it is smaller than the sum of its proper divisors (2473777344).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1216611540 is a wasteful number, since it uses less digits than its factorization.

1216611540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6758968 (or 6758963 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 27.

The square root of 1216611540 is about 34879.9590022695. The cubic root of 1216611540 is about 1067.5395587064.

Adding to 1216611540 its reverse (451166121), we get a palindrome (1667777661).

It can be divided in two parts, 121661 and 1540, that added together give a square (123201 = 351²).

The spelling of 1216611540 in words is "one billion, two hundred sixteen million, six hundred eleven thousand, five hundred forty".