21455429 has 2 divisors, whose sum is σ = 21455430. Its totient is φ = 21455428.

The previous prime is 21455393. The next prime is 21455431. The reversal of 21455429 is 92455412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12888100 + 8567329 = 3590^2 + 2927^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21455429 is a prime.

Together with 21455431, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21455395 and 21455404.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21455459) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10727714 + 10727715.

It is an arithmetic number, because the mean of its divisors is an integer number (10727715).

Almost surely, 2^21455429 is an apocalyptic number.

It is an amenable number.

21455429 is a deficient number, since it is larger than the sum of its proper divisors (1).

21455429 is an equidigital number, since it uses as much as digits as its factorization.

21455429 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 14400, while the sum is 32.

The square root of 21455429 is about 4632.0005397236. Note that the first 3 decimals coincide. The cubic root of 21455429 is about 277.8726060888.

It can be divided in two parts, 21455 and 429, that multiplied together give a triangular number (9204195 = T₄₂₉₀).

The spelling of 21455429 in words is "twenty-one million, four hundred fifty-five thousand, four hundred twenty-nine".