21409955 has 16 divisors (see below), whose sum is σ = 29452224. Its totient is φ = 14636160.

The previous prime is 21409931. The next prime is 21409991. The reversal of 21409955 is 55990412.

It is not a de Polignac number, because 21409955 - 2⁸ = 21409699 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14009 + ... + 15461.

It is an arithmetic number, because the mean of its divisors is an integer number (1840764).

Almost surely, 2^21409955 is an apocalyptic number.

21409955 is a deficient number, since it is larger than the sum of its proper divisors (8042269).

21409955 is a wasteful number, since it uses less digits than its factorization.

21409955 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1886.

The product of its (nonzero) digits is 16200, while the sum is 35.

The square root of 21409955 is about 4627.0892578380. The cubic root of 21409955 is about 277.6761536108.

The spelling of 21409955 in words is "twenty-one million, four hundred nine thousand, nine hundred fifty-five".