21411721 has 12 divisors (see below), whose sum is σ = 23287792. Its totient is φ = 19672128.

The previous prime is 21411713. The next prime is 21411737. The reversal of 21411721 is 12711412.

It is not a de Polignac number, because 21411721 - 2³ = 21411713 is a prime.

It is a super-3 number, since 3×21411721³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21411701) 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 11 ways as a sum of consecutive naturals, for example, 11566 + ... + 13288.

Almost surely, 2^21411721 is an apocalyptic number.

It is an amenable number.

21411721 is a deficient number, since it is larger than the sum of its proper divisors (1876071).

21411721 is a wasteful number, since it uses less digits than its factorization.

21411721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1800 (or 1783 counting only the distinct ones).

The product of its digits is 112, while the sum is 19.

The square root of 21411721 is about 4627.2800866168. The cubic root of 21411721 is about 277.6837881062.

It can be divided in two parts, 214 and 11721, that added together give a triangular number (11935 = T₁₅₄).

The spelling of 21411721 in words is "twenty-one million, four hundred eleven thousand, seven hundred twenty-one".