21523007 has 4 divisors (see below), whose sum is σ = 23479656. Its totient is φ = 19566360.

The previous prime is 21523001. The next prime is 21523049. The reversal of 21523007 is 70032512.

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

It is a de Polignac number, because none of the positive numbers 2^k-21523007 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21523007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523001) 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 3 ways as a sum of consecutive naturals, for example, 978308 + ... + 978329.

It is an arithmetic number, because the mean of its divisors is an integer number (5869914).

Almost surely, 2^21523007 is an apocalyptic number.

21523007 is a deficient number, since it is larger than the sum of its proper divisors (1956649).

21523007 is a wasteful number, since it uses less digits than its factorization.

21523007 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1956648.

The product of its (nonzero) digits is 420, while the sum is 20.

The square root of 21523007 is about 4639.2894930151. The cubic root of 21523007 is about 278.1640380670.

Adding to 21523007 its reverse (70032512), we get a palindrome (91555519).

The spelling of 21523007 in words is "twenty-one million, five hundred twenty-three thousand, seven".