21615671 has 16 divisors (see below), whose sum is σ = 27060480. Its totient is φ = 16774080.

The previous prime is 21615667. The next prime is 21615677. The reversal of 21615671 is 17651612.

It is a cyclic number.

It is not a de Polignac number, because 21615671 - 2² = 21615667 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 (21615677) 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 15 ways as a sum of consecutive naturals, for example, 26315 + ... + 27123.

It is an arithmetic number, because the mean of its divisors is an integer number (1691280).

Almost surely, 2^21615671 is an apocalyptic number.

21615671 is a deficient number, since it is larger than the sum of its proper divisors (5444809).

21615671 is a wasteful number, since it uses less digits than its factorization.

21615671 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1174.

The product of its digits is 2520, while the sum is 29.

The square root of 21615671 is about 4649.2656409373. The cubic root of 21615671 is about 278.5626640491.

The spelling of 21615671 in words is "twenty-one million, six hundred fifteen thousand, six hundred seventy-one".