21715455 has 16 divisors (see below), whose sum is σ = 34969824. Its totient is φ = 11506560.

The previous prime is 21715433. The next prime is 21715471. The reversal of 21715455 is 55451712.

It is not a de Polignac number, because 21715455 - 2⁷ = 21715327 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2256 + ... + 6965.

It is an arithmetic number, because the mean of its divisors is an integer number (2185614).

Almost surely, 2^21715455 is an apocalyptic number.

21715455 is a deficient number, since it is larger than the sum of its proper divisors (13254369).

21715455 is a wasteful number, since it uses less digits than its factorization.

21715455 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9386.

The product of its digits is 7000, while the sum is 30.

The square root of 21715455 is about 4659.9844420341. The cubic root of 21715455 is about 278.9906472886.

It can be divided in two parts, 2171 and 5455, that added together give a triangular number (7626 = T₁₂₃).

The spelling of 21715455 in words is "twenty-one million, seven hundred fifteen thousand, four hundred fifty-five".