21311521155 has 24 divisors (see below), whose sum is σ = 36949470480. Its totient is φ = 11363221440.

The previous prime is 21311521141. The next prime is 21311521163. The reversal of 21311521155 is 55112511312.

It is a happy number.

21311521155 is a `hidden beast` number, since 2 + 131 + 1 + 521 + 1 + 5 + 5 = 666.

It is not a de Polignac number, because 21311521155 - 2⁵ = 21311521123 is a prime.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 122056 + ... + 239834.

It is an arithmetic number, because the mean of its divisors is an integer number (1539561270).

Almost surely, 2^21311521155 is an apocalyptic number.

21311521155 is a deficient number, since it is larger than the sum of its proper divisors (15637949325).

21311521155 is a wasteful number, since it uses less digits than its factorization.

21311521155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 121811 (or 121808 counting only the distinct ones).

The product of its digits is 1500, while the sum is 27.

It can be divided in two parts, 213115 and 21155, that added together give a triangular number (234270 = T₆₈₄).

The spelling of 21311521155 in words is "twenty-one billion, three hundred eleven million, five hundred twenty-one thousand, one hundred fifty-five".