21215493 has 16 divisors (see below), whose sum is σ = 33848640. Its totient is φ = 13055472.

The previous prime is 21215489. The next prime is 21215497. The reversal of 21215493 is 39451212.

It is an interprime number because it is at equal distance from previous prime (21215489) and next prime (21215497).

It is not a de Polignac number, because 21215493 - 2² = 21215489 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21215497) 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 in 15 ways as a sum of consecutive naturals, for example, 29871 + ... + 30572.

It is an arithmetic number, because the mean of its divisors is an integer number (2115540).

Almost surely, 2^21215493 is an apocalyptic number.

It is an amenable number.

21215493 is a deficient number, since it is larger than the sum of its proper divisors (12633147).

21215493 is a wasteful number, since it uses less digits than its factorization.

21215493 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60465 (or 60459 counting only the distinct ones).

The product of its digits is 2160, while the sum is 27.

The square root of 21215493 is about 4606.0278983089. The cubic root of 21215493 is about 276.8329045620.

The spelling of 21215493 in words is "twenty-one million, two hundred fifteen thousand, four hundred ninety-three".