21242731537 has 4 divisors (see below), whose sum is σ = 21254647360. Its totient is φ = 21230815716.

The previous prime is 21242731487. The next prime is 21242731577. The reversal of 21242731537 is 73513724212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21242731537 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21242731496 and 21242731505.

It is not an unprimeable number, because it can be changed into a prime (21242731577) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5955237 + ... + 5958802.

It is an arithmetic number, because the mean of its divisors is an integer number (5313661840).

Almost surely, 2^21242731537 is an apocalyptic number.

It is an amenable number.

21242731537 is a deficient number, since it is larger than the sum of its proper divisors (11915823).

21242731537 is a wasteful number, since it uses less digits than its factorization.

21242731537 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11915822.

The product of its digits is 70560, while the sum is 37.

The spelling of 21242731537 in words is "twenty-one billion, two hundred forty-two million, seven hundred thirty-one thousand, five hundred thirty-seven".