21311767720 has 32 divisors (see below), whose sum is σ = 47983988520. Its totient is φ = 8518927360.

The previous prime is 21311767717. The next prime is 21311767727. The reversal of 21311767720 is 2776711312.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 14772457764 + 6539309956 = 121542^2 + 80866^2 .

It is a super-3 number, since 3×21311767720³ (a number of 32 digits) contains 333 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21311767720.

It is not an unprimeable number, because it can be changed into a prime (21311767727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 120637 + ... + 239116.

Almost surely, 2^21311767720 is an apocalyptic number.

21311767720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21311767720 is an abundant number, since it is smaller than the sum of its proper divisors (26672220800).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21311767720 is a wasteful number, since it uses less digits than its factorization.

21311767720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 361245 (or 361241 counting only the distinct ones).

The product of its (nonzero) digits is 24696, while the sum is 37.

The spelling of 21311767720 in words is "twenty-one billion, three hundred eleven million, seven hundred sixty-seven thousand, seven hundred twenty".