21613855 has 8 divisors (see below), whose sum is σ = 26069472. Its totient is φ = 17202528.

The previous prime is 21613841. The next prime is 21613873. The reversal of 21613855 is 55831612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21613855 - 2¹³ = 21605663 is a prime.

It is a super-2 number, since 2×21613855² = 934317455922050, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 11.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9987 + ... + 11956.

It is an arithmetic number, because the mean of its divisors is an integer number (3258684).

Almost surely, 2^21613855 is an apocalyptic number.

21613855 is a deficient number, since it is larger than the sum of its proper divisors (4455617).

21613855 is a wasteful number, since it uses less digits than its factorization.

21613855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22145.

The product of its digits is 7200, while the sum is 31.

The square root of 21613855 is about 4649.0703371749. The cubic root of 21613855 is about 278.5548628576.

The spelling of 21613855 in words is "twenty-one million, six hundred thirteen thousand, eight hundred fifty-five".