21721421537 has 8 divisors (see below), whose sum is σ = 22077565440. Its totient is φ = 21367307520.

The previous prime is 21721421503. The next prime is 21721421563. The reversal of 21721421537 is 73512412712.

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 21721421537 - 2¹⁶ = 21721356001 is a prime.

It is a super-3 number, since 3×21721421537³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21721421497 and 21721421506.

It is not an unprimeable number, because it can be changed into a prime (21721421567) 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, 485888 + ... + 528705.

It is an arithmetic number, because the mean of its divisors is an integer number (2759695680).

Almost surely, 2^21721421537 is an apocalyptic number.

It is an amenable number.

21721421537 is a deficient number, since it is larger than the sum of its proper divisors (356143903).

21721421537 is a wasteful number, since it uses less digits than its factorization.

21721421537 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1014943.

The product of its digits is 23520, while the sum is 35.

The spelling of 21721421537 in words is "twenty-one billion, seven hundred twenty-one million, four hundred twenty-one thousand, five hundred thirty-seven".