21385215 has 28 divisors (see below), whose sum is σ = 38482344. Its totient is φ = 11403504.

The previous prime is 21385211. The next prime is 21385237. The reversal of 21385215 is 51258312.

It is a happy number.

21385215 is a `hidden beast` number, since 2 + 138 + 521 + 5 = 666.

It is not a de Polignac number, because 21385215 - 2² = 21385211 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 (21385211) by changing a digit.

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 27 ways as a sum of consecutive naturals, for example, 712 + ... + 6578.

Almost surely, 2^21385215 is an apocalyptic number.

21385215 is a deficient number, since it is larger than the sum of its proper divisors (17097129).

21385215 is an frugal number, since it uses more digits than its factorization.

21385215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5890 (or 5875 counting only the distinct ones).

The product of its digits is 2400, while the sum is 27.

The square root of 21385215 is about 4624.4150981503. The cubic root of 21385215 is about 277.5691573435.

The spelling of 21385215 in words is "twenty-one million, three hundred eighty-five thousand, two hundred fifteen".