21721895 has 8 divisors (see below), whose sum is σ = 28071456. Its totient is φ = 16040736.

The previous prime is 21721879. The next prime is 21721901. The reversal of 21721895 is 59812712.

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 21721895 - 2⁴ = 21721879 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 167027 + ... + 167156.

It is an arithmetic number, because the mean of its divisors is an integer number (3508932).

Almost surely, 2^21721895 is an apocalyptic number.

21721895 is a deficient number, since it is larger than the sum of its proper divisors (6349561).

21721895 is a wasteful number, since it uses less digits than its factorization.

21721895 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 334201.

The product of its digits is 10080, while the sum is 35.

The square root of 21721895 is about 4660.6753802427. The cubic root of 21721895 is about 279.0182239951.

The spelling of 21721895 in words is "twenty-one million, seven hundred twenty-one thousand, eight hundred ninety-five".