21221367731 has 2 divisors, whose sum is σ = 21221367732. Its totient is φ = 21221367730.

The previous prime is 21221367721. The next prime is 21221367803. The reversal of 21221367731 is 13776312212.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21221367731 - 2²² = 21217173427 is a prime.

It is a super-2 number, since 2×21221367731² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21221367691 and 21221367700.

It is not a weakly prime, because it can be changed into another prime (21221367701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610683865 + 10610683866.

It is an arithmetic number, because the mean of its divisors is an integer number (10610683866).

Almost surely, 2^21221367731 is an apocalyptic number.

21221367731 is a deficient number, since it is larger than the sum of its proper divisors (1).

21221367731 is an equidigital number, since it uses as much as digits as its factorization.

21221367731 is an evil number, because the sum of its binary digits is even.

The product of its digits is 21168, while the sum is 35.

Adding to 21221367731 its reverse (13776312212), we get a palindrome (34997679943).

The spelling of 21221367731 in words is "twenty-one billion, two hundred twenty-one million, three hundred sixty-seven thousand, seven hundred thirty-one".