21720787511 has 8 divisors (see below), whose sum is σ = 23003371440. Its totient is φ = 20438747008.

The previous prime is 21720787481. The next prime is 21720787513. The reversal of 21720787511 is 11578702712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21720787511 - 2⁶ = 21720787447 is a prime.

It is a super-2 number, since 2×21720787511² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21720787513) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 52076 + ... + 214833.

It is an arithmetic number, because the mean of its divisors is an integer number (2875421430).

Almost surely, 2^21720787511 is an apocalyptic number.

21720787511 is a deficient number, since it is larger than the sum of its proper divisors (1282583929).

21720787511 is a wasteful number, since it uses less digits than its factorization.

21720787511 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 271713.

The product of its (nonzero) digits is 54880, while the sum is 41.

The spelling of 21720787511 in words is "twenty-one billion, seven hundred twenty million, seven hundred eighty-seven thousand, five hundred eleven".