21742405 has 16 divisors (see below), whose sum is σ = 27771120. Its totient is φ = 16284672.

The previous prime is 21742381. The next prime is 21742411. The reversal of 21742405 is 50424712.

It can be written as a sum of positive squares in 8 ways, for example, as 54756 + 21687649 = 234^2 + 4657^2 .

It is a cyclic number.

It is not a de Polignac number, because 21742405 - 2¹³ = 21734213 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21742405.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18907 + ... + 20023.

It is an arithmetic number, because the mean of its divisors is an integer number (1735695).

Almost surely, 2^21742405 is an apocalyptic number.

It is an amenable number.

21742405 is a deficient number, since it is larger than the sum of its proper divisors (6028715).

21742405 is a wasteful number, since it uses less digits than its factorization.

21742405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1368.

The product of its (nonzero) digits is 2240, while the sum is 25.

The square root of 21742405 is about 4662.8751859770. The cubic root of 21742405 is about 279.1060135056.

The spelling of 21742405 in words is "twenty-one million, seven hundred forty-two thousand, four hundred five".