21615673 has 4 divisors (see below), whose sum is σ = 22753360. Its totient is φ = 20477988.

The previous prime is 21615667. The next prime is 21615677. The reversal of 21615673 is 37651612.

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 21615673 - 2⁵ = 21615641 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21615677) 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, 568815 + ... + 568852.

It is an arithmetic number, because the mean of its divisors is an integer number (5688340).

Almost surely, 2^21615673 is an apocalyptic number.

It is an amenable number.

21615673 is a deficient number, since it is larger than the sum of its proper divisors (1137687).

21615673 is a wasteful number, since it uses less digits than its factorization.

21615673 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1137686.

The product of its digits is 7560, while the sum is 31.

The square root of 21615673 is about 4649.2658560250. The cubic root of 21615673 is about 278.5626726405.

The spelling of 21615673 in words is "twenty-one million, six hundred fifteen thousand, six hundred seventy-three".