21612047 has 4 divisors (see below), whose sum is σ = 22357320. Its totient is φ = 20866776.

The previous prime is 21612037. The next prime is 21612061. The reversal of 21612047 is 74021612.

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

It is not a de Polignac number, because 21612047 - 2⁸ = 21611791 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 (21612037) 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, 372593 + ... + 372650.

It is an arithmetic number, because the mean of its divisors is an integer number (5589330).

Almost surely, 2^21612047 is an apocalyptic number.

21612047 is a deficient number, since it is larger than the sum of its proper divisors (745273).

21612047 is an equidigital number, since it uses as much as digits as its factorization.

21612047 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 745272.

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 21612047 is about 4648.8758856308. The cubic root of 21612047 is about 278.5470955985.

Adding to 21612047 its reverse (74021612), we get a palindrome (95633659).

The spelling of 21612047 in words is "twenty-one million, six hundred twelve thousand, forty-seven".