21135415723 has 4 divisors (see below), whose sum is σ = 21137230960. Its totient is φ = 21133600488.

The previous prime is 21135415703. The next prime is 21135415751. The reversal of 21135415723 is 32751453112.

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

It is a cyclic number.

It is not a de Polignac number, because 21135415723 - 2⁹ = 21135415211 is a prime.

It is a super-3 number, since 3×21135415723³ (a number of 32 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21135415703) 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, 890040 + ... + 913477.

It is an arithmetic number, because the mean of its divisors is an integer number (5284307740).

Almost surely, 2^21135415723 is an apocalyptic number.

21135415723 is a deficient number, since it is larger than the sum of its proper divisors (1815237).

21135415723 is a wasteful number, since it uses less digits than its factorization.

21135415723 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1815236.

The product of its digits is 25200, while the sum is 34.

Adding to 21135415723 its reverse (32751453112), we get a palindrome (53886868835).

The spelling of 21135415723 in words is "twenty-one billion, one hundred thirty-five million, four hundred fifteen thousand, seven hundred twenty-three".