21349021 has 6 divisors (see below), whose sum is σ = 21580890. Its totient is φ = 21119616.

The previous prime is 21349019. The next prime is 21349033. The reversal of 21349021 is 12094312.

It can be written as a sum of positive squares in 3 ways, for example, as 60025 + 21288996 = 245^2 + 4614^2 .

It is not a de Polignac number, because 21349021 - 2¹ = 21349019 is a prime.

It is the 4621-st Hogben number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21348983 and 21349001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21349001) by changing a digit.

It is a nontrivial repunit in base 4620.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 8275 + ... + 10543.

It is an arithmetic number, because the mean of its divisors is an integer number (3596815).

Almost surely, 2^21349021 is an apocalyptic number.

It is an amenable number.

21349021 is a deficient number, since it is larger than the sum of its proper divisors (231869).

21349021 is an frugal number, since it uses more digits than its factorization.

21349021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2463 (or 2366 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 21349021 is about 4620.5000811600. The cubic root of 21349021 is about 277.4124757116.

The spelling of 21349021 in words is "twenty-one million, three hundred forty-nine thousand, twenty-one".