21506073 has 4 divisors (see below), whose sum is σ = 28674768. Its totient is φ = 14337380.

The previous prime is 21506059. The next prime is 21506083. The reversal of 21506073 is 37060512.

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 a cyclic number.

It is not a de Polignac number, because 21506073 - 2⁵ = 21506041 is a prime.

It is a super-2 number, since 2×21506073² = 925022351762658, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21506083) 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, 3584343 + ... + 3584348.

It is an arithmetic number, because the mean of its divisors is an integer number (7168692).

Almost surely, 2^21506073 is an apocalyptic number.

It is an amenable number.

21506073 is a deficient number, since it is larger than the sum of its proper divisors (7168695).

21506073 is an equidigital number, since it uses as much as digits as its factorization.

21506073 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7168694.

The product of its (nonzero) digits is 1260, while the sum is 24.

The square root of 21506073 is about 4637.4640699417. The cubic root of 21506073 is about 278.0910670717.

Adding to 21506073 its reverse (37060512), we get a palindrome (58566585).

The spelling of 21506073 in words is "twenty-one million, five hundred six thousand, seventy-three".