21089731 has 4 divisors (see below), whose sum is σ = 22712032. Its totient is φ = 19467432.

The previous prime is 21089729. The next prime is 21089749. The reversal of 21089731 is 13798012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21089731 - 2¹ = 21089729 is a prime.

It is a super-2 number, since 2×21089731² = 889553507304722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21089693 and 21089702.

It is not an unprimeable number, because it can be changed into a prime (21089711) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 811131 + ... + 811156.

It is an arithmetic number, because the mean of its divisors is an integer number (5678008).

Almost surely, 2^21089731 is an apocalyptic number.

21089731 is a deficient number, since it is larger than the sum of its proper divisors (1622301).

21089731 is a wasteful number, since it uses less digits than its factorization.

21089731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1622300.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 21089731 is about 4592.3557135745. The cubic root of 21089731 is about 276.2848132863.

The spelling of 21089731 in words is "twenty-one million, eighty-nine thousand, seven hundred thirty-one".