21508901 has 8 divisors (see below), whose sum is σ = 22080960. Its totient is φ = 20940192.

The previous prime is 21508891. The next prime is 21508919. The reversal of 21508901 is 10980512.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21508901 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 (21508601) 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, 16976 + ... + 18198.

It is an arithmetic number, because the mean of its divisors is an integer number (2760120).

Almost surely, 2^21508901 is an apocalyptic number.

It is an amenable number.

21508901 is a deficient number, since it is larger than the sum of its proper divisors (572059).

21508901 is a wasteful number, since it uses less digits than its factorization.

21508901 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1675.

The product of its (nonzero) digits is 720, while the sum is 26.

The square root of 21508901 is about 4637.7689679414. The cubic root of 21508901 is about 278.1032559864.

The spelling of 21508901 in words is "twenty-one million, five hundred eight thousand, nine hundred one".