21613391 has 8 divisors (see below), whose sum is σ = 22246224. Its totient is φ = 20986560.

The previous prime is 21613379. The next prime is 21613421. The reversal of 21613391 is 19331612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21613391 - 2⁶ = 21613327 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21613391.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21613321) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6395 + ... + 9171.

It is an arithmetic number, because the mean of its divisors is an integer number (2780778).

Almost surely, 2^21613391 is an apocalyptic number.

21613391 is a deficient number, since it is larger than the sum of its proper divisors (632833).

21613391 is a wasteful number, since it uses less digits than its factorization.

21613391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3001.

The product of its digits is 972, while the sum is 26.

The square root of 21613391 is about 4649.0204344571. The cubic root of 21613391 is about 278.5528695316.

The spelling of 21613391 in words is "twenty-one million, six hundred thirteen thousand, three hundred ninety-one".