21906143 has 16 divisors (see below), whose sum is σ = 26397696. Its totient is φ = 17772480.

The previous prime is 21906113. The next prime is 21906151. The reversal of 21906143 is 34160912.

It is a cyclic number.

It is not a de Polignac number, because 21906143 - 2¹⁶ = 21840607 is a prime.

It is a super-2 number, since 2×21906143² = 959758202272898, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21906113) 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, 15923 + ... + 17243.

It is an arithmetic number, because the mean of its divisors is an integer number (1649856).

Almost surely, 2^21906143 is an apocalyptic number.

21906143 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

21906143 is a deficient number, since it is larger than the sum of its proper divisors (4491553).

21906143 is a wasteful number, since it uses less digits than its factorization.

21906143 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1454.

The product of its (nonzero) digits is 1296, while the sum is 26.

The square root of 21906143 is about 4680.3998760790. The cubic root of 21906143 is about 279.8048938420.

The spelling of 21906143 in words is "twenty-one million, nine hundred six thousand, one hundred forty-three".