21231431731 has 2 divisors, whose sum is σ = 21231431732. Its totient is φ = 21231431730.

The previous prime is 21231431681. The next prime is 21231431737. The reversal of 21231431731 is 13713413212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21231431731 - 2⁷ = 21231431603 is a prime.

It is a super-2 number, since 2×21231431731² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21231431731.

It is not a weakly prime, because it can be changed into another prime (21231431737) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10615715865 + 10615715866.

It is an arithmetic number, because the mean of its divisors is an integer number (10615715866).

Almost surely, 2^21231431731 is an apocalyptic number.

21231431731 is a deficient number, since it is larger than the sum of its proper divisors (1).

21231431731 is an equidigital number, since it uses as much as digits as its factorization.

21231431731 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3024, while the sum is 28.

Adding to 21231431731 its reverse (13713413212), we get a palindrome (34944844943).

The spelling of 21231431731 in words is "twenty-one billion, two hundred thirty-one million, four hundred thirty-one thousand, seven hundred thirty-one".