21455423 has 16 divisors (see below), whose sum is σ = 24246432. Its totient is φ = 18816000.

The previous prime is 21455393. The next prime is 21455429. The reversal of 21455423 is 32455412.

It is a happy number.

It is a Cunningham number, because it is equal to 4632²-1.

It is a cyclic number.

It is not a de Polignac number, because 21455423 - 2¹⁶ = 21389887 is a prime.

It is a super-2 number, since 2×21455423² = 920670352217858, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21455392 and 21455401.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21455429) 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, 50753 + ... + 51173.

It is an arithmetic number, because the mean of its divisors is an integer number (1515402).

Almost surely, 2^21455423 is an apocalyptic number.

21455423 is a deficient number, since it is larger than the sum of its proper divisors (2791009).

21455423 is a wasteful number, since it uses less digits than its factorization.

21455423 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 586.

The product of its digits is 4800, while the sum is 26.

The square root of 21455423 is about 4631.9998920553. Note that the first 3 decimals coincide. The cubic root of 21455423 is about 277.8725801865.

The spelling of 21455423 in words is "twenty-one million, four hundred fifty-five thousand, four hundred twenty-three".