21655213 has 16 divisors (see below), whose sum is σ = 23328000. Its totient is φ = 20056960.

The previous prime is 21655211. The next prime is 21655219. The reversal of 21655213 is 31255612.

It is a cyclic number.

It is not a de Polignac number, because 21655213 - 2¹ = 21655211 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21655211) 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, 145263 + ... + 145411.

It is an arithmetic number, because the mean of its divisors is an integer number (1458000).

Almost surely, 2^21655213 is an apocalyptic number.

21655213 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

It is an amenable number.

21655213 is a deficient number, since it is larger than the sum of its proper divisors (1672787).

21655213 is a wasteful number, since it uses less digits than its factorization.

21655213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 332.

The product of its digits is 1800, while the sum is 25.

The square root of 21655213 is about 4653.5161974576. The cubic root of 21655213 is about 278.7324207512.

The spelling of 21655213 in words is "twenty-one million, six hundred fifty-five thousand, two hundred thirteen".