21471639 has 16 divisors (see below), whose sum is σ = 32828160. Its totient is φ = 12228480.

The previous prime is 21471631. The next prime is 21471641. The reversal of 21471639 is 93617412.

It is not a de Polignac number, because 21471639 - 2³ = 21471631 is a prime.

It is a super-2 number, since 2×21471639² = 922062562692642, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21471631) 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, 5407 + ... + 8495.

It is an arithmetic number, because the mean of its divisors is an integer number (2051760).

Almost surely, 2^21471639 is an apocalyptic number.

21471639 is a deficient number, since it is larger than the sum of its proper divisors (11356521).

21471639 is a wasteful number, since it uses less digits than its factorization.

21471639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3430.

The product of its digits is 9072, while the sum is 33.

The square root of 21471639 is about 4633.7499932560. The cubic root of 21471639 is about 277.9425678850.

The spelling of 21471639 in words is "twenty-one million, four hundred seventy-one thousand, six hundred thirty-nine".