1221500005155 has 12 divisors (see below), whose sum is σ = 2117266675680. Its totient is φ = 651466669392.

The previous prime is 1221500005129. The next prime is 1221500005267. The reversal of 1221500005155 is 5515000051221.

1221500005155 is a `hidden beast` number, since 1 + 2 + 2 + 1 + 500 + 0 + 0 + 5 + 155 = 666.

It is not a de Polignac number, because 1221500005155 - 2¹⁶ = 1221499939619 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 13572222235 + ... + 13572222324.

It is an arithmetic number, because the mean of its divisors is an integer number (176438889640).

Almost surely, 2^{1221500005155} is an apocalyptic number.

1221500005155 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

1221500005155 is a deficient number, since it is larger than the sum of its proper divisors (895766670525).

1221500005155 is a wasteful number, since it uses less digits than its factorization.

1221500005155 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27144444570 (or 27144444567 counting only the distinct ones).

The product of its (nonzero) digits is 2500, while the sum is 27.

Adding to 1221500005155 its reverse (5515000051221), we get a palindrome (6736500056376).

The spelling of 1221500005155 in words is "one trillion, two hundred twenty-one billion, five hundred million, five thousand, one hundred fifty-five".