21680501049 has 9 divisors (see below), whose sum is σ = 31316917359. Its totient is φ = 14453372880.

The previous prime is 21680501023. The next prime is 21680501083. The reversal of 21680501049 is 94010508612.

The square root of 21680501049 is 147243.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 11005478649 + 10675022400 = 104907^2 + 103320^2 .

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 21680501049 - 2⁷ = 21680500921 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21680501009) by changing a digit.

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 8 ways as a sum of consecutive naturals, for example, 417189 + ... + 466269.

Almost surely, 2^21680501049 is an apocalyptic number.

21680501049 is the 147243-rd square number.

21680501049 is the 73622-nd centered octagonal number.

It is an amenable number.

21680501049 is a deficient number, since it is larger than the sum of its proper divisors (9636416310).

21680501049 is an frugal number, since it uses more digits than its factorization.

21680501049 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 98168 (or 49084 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

Multiplying 21680501049 by its sum of digits (36), we get a square (780498037764 = 883458²).

It can be divided in two parts, 21680 and 501049, that added together give a square (522729 = 723²).

The spelling of 21680501049 in words is "twenty-one billion, six hundred eighty million, five hundred one thousand, forty-nine".