1216402781 has 16 divisors (see below), whose sum is σ = 1397990400. Its totient is φ = 1046746800.

The previous prime is 1216402721. The next prime is 1216402799. The reversal of 1216402781 is 1872046121.

It is a happy number.

It is a de Polignac number, because none of the positive numbers 2^k-1216402781 is a prime.

It is a super-2 number, since 2×1216402781² = 2959271451249067922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1216402721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 454076 + ... + 456746.

It is an arithmetic number, because the mean of its divisors is an integer number (87374400).

Almost surely, 2^1216402781 is an apocalyptic number.

1216402781 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1216402781 is a deficient number, since it is larger than the sum of its proper divisors (181587619).

1216402781 is a wasteful number, since it uses less digits than its factorization.

1216402781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4880.

The product of its (nonzero) digits is 5376, while the sum is 32.

The square root of 1216402781 is about 34876.9663388317. The cubic root of 1216402781 is about 1067.4784953263.

It can be divided in two parts, 121640 and 2781, that added together give a palindrome (124421).

The spelling of 1216402781 in words is "one billion, two hundred sixteen million, four hundred two thousand, seven hundred eighty-one".