21523061 has 4 divisors (see below), whose sum is σ = 24597792. Its totient is φ = 18448332.

The previous prime is 21523049. The next prime is 21523063. The reversal of 21523061 is 16032512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21523061 - 2¹⁰ = 21522037 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523063) 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, 1537355 + ... + 1537368.

It is an arithmetic number, because the mean of its divisors is an integer number (6149448).

Almost surely, 2^21523061 is an apocalyptic number.

It is an amenable number.

21523061 is a deficient number, since it is larger than the sum of its proper divisors (3074731).

21523061 is an equidigital number, since it uses as much as digits as its factorization.

21523061 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3074730.

The product of its (nonzero) digits is 360, while the sum is 20.

The square root of 21523061 is about 4639.2953128681. The cubic root of 21523061 is about 278.1642706994.

Adding to 21523061 its reverse (16032512), we get a palindrome (37555573).

The spelling of 21523061 in words is "twenty-one million, five hundred twenty-three thousand, sixty-one".