21851688668502 has 32 divisors (see below), whose sum is σ = 54487327590144. Its totient is φ = 5675763290400.

The previous prime is 21851688668483. The next prime is 21851688668549. The reversal of 21851688668502 is 20586688615812.

It is a Harshad number since it is a multiple of its sum of digits (66).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 23649013249 + ... + 23649014172.

It is an arithmetic number, because the mean of its divisors is an integer number (1702728987192).

Almost surely, 2^{21851688668502} is an apocalyptic number.

21851688668502 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

21851688668502 is an abundant number, since it is smaller than the sum of its proper divisors (32635638921642).

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

21851688668502 is a wasteful number, since it uses less digits than its factorization.

21851688668502 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47298027444.

The product of its (nonzero) digits is 88473600, while the sum is 66.

The spelling of 21851688668502 in words is "twenty-one trillion, eight hundred fifty-one billion, six hundred eighty-eight million, six hundred sixty-eight thousand, five hundred two".