21640781556988 has 48 divisors (see below), whose sum is σ = 43111127678976. Its totient is φ = 9408896228160.

The previous prime is 21640781556983. The next prime is 21640781556991. The reversal of 21640781556988 is 88965518704612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21640781556983) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 98877445 + ... + 99096067.

It is an arithmetic number, because the mean of its divisors is an integer number (898148493312).

Almost surely, 2^{21640781556988} is an apocalyptic number.

It is an amenable number.

21640781556988 is a deficient number, since it is larger than the sum of its proper divisors (21470346121988).

21640781556988 is a wasteful number, since it uses less digits than its factorization.

21640781556988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 316474 (or 316472 counting only the distinct ones).

The product of its (nonzero) digits is 232243200, while the sum is 70.

The spelling of 21640781556988 in words is "twenty-one trillion, six hundred forty billion, seven hundred eighty-one million, five hundred fifty-six thousand, nine hundred eighty-eight".