21680506737 has 20 divisors (see below), whose sum is σ = 32403918580. Its totient is φ = 14446089504.

The previous prime is 21680506699. The next prime is 21680506741. The reversal of 21680506737 is 73760508612.

It can be written as a sum of positive squares in 2 ways, for example, as 11594120976 + 10086385761 = 107676^2 + 100431^2 .

It is not a de Polignac number, because 21680506737 - 2¹⁰ = 21680505713 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21680506692 and 21680506701.

It is not an unprimeable number, because it can be changed into a prime (21680502737) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 87339 + ... + 225807.

It is an arithmetic number, because the mean of its divisors is an integer number (1620195929).

Almost surely, 2^21680506737 is an apocalyptic number.

21680506737 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21680506737 is a deficient number, since it is larger than the sum of its proper divisors (10723411843).

21680506737 is a wasteful number, since it uses less digits than its factorization.

21680506737 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 140414 (or 140405 counting only the distinct ones).

The product of its (nonzero) digits is 423360, while the sum is 45.

The spelling of 21680506737 in words is "twenty-one billion, six hundred eighty million, five hundred six thousand, seven hundred thirty-seven".