21640143 has 16 divisors (see below), whose sum is σ = 33130496. Its totient is φ = 12307680.

The previous prime is 21640141. The next prime is 21640147. The reversal of 21640143 is 34104612.

It is not a de Polignac number, because 21640143 - 2¹ = 21640141 is a prime.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21640141) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2373 + ... + 6993.

It is an arithmetic number, because the mean of its divisors is an integer number (2070656).

Almost surely, 2^21640143 is an apocalyptic number.

21640143 is a deficient number, since it is larger than the sum of its proper divisors (11490353).

21640143 is a wasteful number, since it uses less digits than its factorization.

21640143 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4854.

The product of its (nonzero) digits is 576, while the sum is 21.

The square root of 21640143 is about 4651.8967099453. The cubic root of 21640143 is about 278.6677485275.

Adding to 21640143 its reverse (34104612), we get a palindrome (55744755).

The spelling of 21640143 in words is "twenty-one million, six hundred forty thousand, one hundred forty-three".