21720705587 has 16 divisors (see below), whose sum is σ = 25435167744. Its totient is φ = 18159336000.

The previous prime is 21720705583. The next prime is 21720705599. The reversal of 21720705587 is 78550702712.

It is a cyclic number.

It is not a de Polignac number, because 21720705587 - 2² = 21720705583 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21720705581) 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, 1914662 + ... + 1925972.

It is an arithmetic number, because the mean of its divisors is an integer number (1589697984).

Almost surely, 2^21720705587 is an apocalyptic number.

21720705587 is a deficient number, since it is larger than the sum of its proper divisors (3714462157).

21720705587 is a wasteful number, since it uses less digits than its factorization.

21720705587 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18050.

The product of its (nonzero) digits is 274400, while the sum is 44.

The spelling of 21720705587 in words is "twenty-one billion, seven hundred twenty million, seven hundred five thousand, five hundred eighty-seven".