21611955 has 16 divisors (see below), whose sum is σ = 34997760. Its totient is φ = 11386848.

The previous prime is 21611939. The next prime is 21611957. The reversal of 21611955 is 55911612.

It is not a de Polignac number, because 21611955 - 2⁴ = 21611939 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21611957) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7435 + ... + 9924.

It is an arithmetic number, because the mean of its divisors is an integer number (2187360).

Almost surely, 2^21611955 is an apocalyptic number.

21611955 is a deficient number, since it is larger than the sum of its proper divisors (13385805).

21611955 is a wasteful number, since it uses less digits than its factorization.

21611955 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17450.

The product of its digits is 2700, while the sum is 30.

The square root of 21611955 is about 4648.8659907552. The cubic root of 21611955 is about 278.5467003503.

The spelling of 21611955 in words is "twenty-one million, six hundred eleven thousand, nine hundred fifty-five".