21151723 has 16 divisors (see below), whose sum is σ = 23030784. Its totient is φ = 19353600.

The previous prime is 21151721. The next prime is 21151733. The reversal of 21151723 is 32715112.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21151723 - 2¹ = 21151721 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21151694 and 21151703.

It is not an unprimeable number, because it can be changed into a prime (21151721) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 166486 + ... + 166612.

It is an arithmetic number, because the mean of its divisors is an integer number (1439424).

Almost surely, 2^21151723 is an apocalyptic number.

21151723 is a deficient number, since it is larger than the sum of its proper divisors (1879061).

21151723 is a wasteful number, since it uses less digits than its factorization.

21151723 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 342.

The product of its digits is 420, while the sum is 22.

The square root of 21151723 is about 4599.1002380901. The cubic root of 21151723 is about 276.5552560244. Note that the first 3 decimals are identical.

Adding to 21151723 its reverse (32715112), we get a palindrome (53866835).

The spelling of 21151723 in words is "twenty-one million, one hundred fifty-one thousand, seven hundred twenty-three".