21345731 has 12 divisors (see below), whose sum is σ = 23821896. Its totient is φ = 19108320.

The previous prime is 21345719. The next prime is 21345733. The reversal of 21345731 is 13754312.

It is a de Polignac number, because none of the positive numbers 2^k-21345731 is a prime.

It is a super-2 number, since 2×21345731² = 911280463848722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21345731.

It is not an unprimeable number, because it can be changed into a prime (21345733) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6791 + ... + 9423.

It is an arithmetic number, because the mean of its divisors is an integer number (1985158).

Almost surely, 2^21345731 is an apocalyptic number.

21345731 is a deficient number, since it is larger than the sum of its proper divisors (2476165).

21345731 is a wasteful number, since it uses less digits than its factorization.

21345731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2722 (or 2711 counting only the distinct ones).

The product of its digits is 2520, while the sum is 26.

The square root of 21345731 is about 4620.1440453735. The cubic root of 21345731 is about 277.3982247235.

The spelling of 21345731 in words is "twenty-one million, three hundred forty-five thousand, seven hundred thirty-one".