21136723 has 2 divisors, whose sum is σ = 21136724. Its totient is φ = 21136722.

The previous prime is 21136681. The next prime is 21136751. The reversal of 21136723 is 32763112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21136723 - 2⁹ = 21136211 is a prime.

It is a super-2 number, since 2×21136723² = 893522118357458, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21136783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10568361 + 10568362.

It is an arithmetic number, because the mean of its divisors is an integer number (10568362).

Almost surely, 2^21136723 is an apocalyptic number.

21136723 is a deficient number, since it is larger than the sum of its proper divisors (1).

21136723 is an equidigital number, since it uses as much as digits as its factorization.

21136723 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1512, while the sum is 25.

The square root of 21136723 is about 4597.4691951116. The cubic root of 21136723 is about 276.4898663973.

Adding to 21136723 its reverse (32763112), we get a palindrome (53899835).

It can be divided in two parts, 2113 and 6723, that added together give a square (8836 = 94²).

The spelling of 21136723 in words is "twenty-one million, one hundred thirty-six thousand, seven hundred twenty-three".