21161724 has 12 divisors (see below), whose sum is σ = 49377384. Its totient is φ = 7053904.

The previous prime is 21161717. The next prime is 21161729. The reversal of 21161724 is 42716112.

It is a tau number, because it is divible by the number of its divisors (12).

It is a junction number, because it is equal to n+sod(n) for n = 21161694 and 21161703.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21161729) 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, 881727 + ... + 881750.

It is an arithmetic number, because the mean of its divisors is an integer number (4114782).

Almost surely, 2^21161724 is an apocalyptic number.

It is an amenable number.

21161724 is an abundant number, since it is smaller than the sum of its proper divisors (28215660).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21161724 is a wasteful number, since it uses less digits than its factorization.

21161724 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1763484 (or 1763482 counting only the distinct ones).

The product of its digits is 672, while the sum is 24.

The square root of 21161724 is about 4600.1873874876. The cubic root of 21161724 is about 276.5988362931.

Adding to 21161724 its reverse (42716112), we get a palindrome (63877836).

The spelling of 21161724 in words is "twenty-one million, one hundred sixty-one thousand, seven hundred twenty-four".