21151551660 has 24 divisors (see below), whose sum is σ = 59224344816. Its totient is φ = 5640413760.

The previous prime is 21151551653. The next prime is 21151551661. The reversal of 21151551660 is 6615515112.

It is not an unprimeable number, because it can be changed into a prime (21151551661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 176262871 + ... + 176262990.

It is an arithmetic number, because the mean of its divisors is an integer number (2467681034).

Almost surely, 2^21151551660 is an apocalyptic number.

21151551660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21151551660 is an abundant number, since it is smaller than the sum of its proper divisors (38072793156).

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

21151551660 is a wasteful number, since it uses less digits than its factorization.

21151551660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 352525873 (or 352525871 counting only the distinct ones).

The product of its (nonzero) digits is 9000, while the sum is 33.

It can be divided in two parts, 211515 and 51660, that added together give a triangular number (263175 = T₇₂₅).

The spelling of 21151551660 in words is "twenty-one billion, one hundred fifty-one million, five hundred fifty-one thousand, six hundred sixty".