20721187499 has 2 divisors, whose sum is σ = 20721187500. Its totient is φ = 20721187498.

The previous prime is 20721187469. The next prime is 20721187507. The reversal of 20721187499 is 99478112702.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20721187499 - 2¹² = 20721183403 is a prime.

It is a super-2 number, since 2×20721187499² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20721187469) 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 as a sum of consecutive naturals, namely, 10360593749 + 10360593750.

It is an arithmetic number, because the mean of its divisors is an integer number (10360593750).

Almost surely, 2^20721187499 is an apocalyptic number.

20721187499 is a deficient number, since it is larger than the sum of its proper divisors (1).

20721187499 is an equidigital number, since it uses as much as digits as its factorization.

20721187499 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 508032, while the sum is 50.

The spelling of 20721187499 in words is "twenty billion, seven hundred twenty-one million, one hundred eighty-seven thousand, four hundred ninety-nine".