21653001 has 12 divisors (see below), whose sum is σ = 32435312. Its totient is φ = 14435172.

The previous prime is 21652997. The next prime is 21653011. The reversal of 21653001 is 10035612.

It is not a de Polignac number, because 21653001 - 2² = 21652997 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21653011) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 44311 + ... + 44796.

Almost surely, 2^21653001 is an apocalyptic number.

It is an amenable number.

21653001 is a deficient number, since it is larger than the sum of its proper divisors (10782311).

21653001 is an frugal number, since it uses more digits than its factorization.

21653001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89122 (or 89110 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 18.

The square root of 21653001 is about 4653.2785216447. The cubic root of 21653001 is about 278.7229299324.

Adding to 21653001 its reverse (10035612), we get a palindrome (31688613).

The spelling of 21653001 in words is "twenty-one million, six hundred fifty-three thousand, one".