21721995 has 12 divisors (see below), whose sum is σ = 37651536. Its totient is φ = 11585040.

The previous prime is 21721981. The next prime is 21722011. The reversal of 21721995 is 59912712.

It is not a de Polignac number, because 21721995 - 2¹⁷ = 21590923 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 241311 + ... + 241400.

It is an arithmetic number, because the mean of its divisors is an integer number (3137628).

Almost surely, 2^21721995 is an apocalyptic number.

21721995 is a deficient number, since it is larger than the sum of its proper divisors (15929541).

21721995 is a wasteful number, since it uses less digits than its factorization.

21721995 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 482722 (or 482719 counting only the distinct ones).

The product of its digits is 11340, while the sum is 36.

The square root of 21721995 is about 4660.6861082892. The cubic root of 21721995 is about 279.0186521619.

The spelling of 21721995 in words is "twenty-one million, seven hundred twenty-one thousand, nine hundred ninety-five".