21408867731 has 4 divisors (see below), whose sum is σ = 21550648464. Its totient is φ = 21267087000.

The previous prime is 21408867719. The next prime is 21408867749. The reversal of 21408867731 is 13776880412.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21408867731 is a prime.

It is a super-2 number, since 2×21408867731² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21408867631) 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 3 ways as a sum of consecutive naturals, for example, 70890140 + ... + 70890441.

It is an arithmetic number, because the mean of its divisors is an integer number (5387662116).

Almost surely, 2^21408867731 is an apocalyptic number.

21408867731 is a deficient number, since it is larger than the sum of its proper divisors (141780733).

21408867731 is a wasteful number, since it uses less digits than its factorization.

21408867731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 141780732.

The product of its (nonzero) digits is 451584, while the sum is 47.

The spelling of 21408867731 in words is "twenty-one billion, four hundred eight million, eight hundred sixty-seven thousand, seven hundred thirty-one".