21655011 has 24 divisors (see below), whose sum is σ = 34416144. Its totient is φ = 12069120.

The previous prime is 21655009. The next prime is 21655031. The reversal of 21655011 is 11055612.

It is not a de Polignac number, because 21655011 - 2¹ = 21655009 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is not an unprimeable number, because it can be changed into a prime (21655001) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4231 + ... + 7823.

It is an arithmetic number, because the mean of its divisors is an integer number (1434006).

Almost surely, 2^21655011 is an apocalyptic number.

21655011 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21655011 is a deficient number, since it is larger than the sum of its proper divisors (12761133).

21655011 is a wasteful number, since it uses less digits than its factorization.

21655011 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3651 (or 3644 counting only the distinct ones).

The product of its (nonzero) digits is 300, while the sum is 21.

The square root of 21655011 is about 4653.4944933888. The cubic root of 21655011 is about 278.7315540758.

The spelling of 21655011 in words is "twenty-one million, six hundred fifty-five thousand, eleven".