21661321601612 has 36 divisors (see below), whose sum is σ = 48105012912264. Its totient is φ = 8439475947840.

The previous prime is 21661321601573. The next prime is 21661321601651. The reversal of 21661321601612 is 21610612316612.

It is an interprime number because it is at equal distance from previous prime (21661321601573) and next prime (21661321601651).

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, 5023495433 + ... + 5023499744.

It is an arithmetic number, because the mean of its divisors is an integer number (1336250358674).

Almost surely, 2^{21661321601612} is an apocalyptic number.

21661321601612 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

21661321601612 is an abundant number, since it is smaller than the sum of its proper divisors (26443691310652).

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

21661321601612 is a wasteful number, since it uses less digits than its factorization.

21661321601612 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10046995206 (or 10046995197 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 38.

The spelling of 21661321601612 in words is "twenty-one trillion, six hundred sixty-one billion, three hundred twenty-one million, six hundred one thousand, six hundred twelve".