21900001 has 4 divisors (see below), whose sum is σ = 21987504. Its totient is φ = 21812500.

The previous prime is 21899987. The next prime is 21900013. The reversal of 21900001 is 10000912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21900001 is a prime.

It is a super-2 number, since 2×21900001² = 959220087600002, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21900031) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 43375 + ... + 43876.

It is an arithmetic number, because the mean of its divisors is an integer number (5496876).

Almost surely, 2^21900001 is an apocalyptic number.

It is an amenable number.

21900001 is a deficient number, since it is larger than the sum of its proper divisors (87503).

21900001 is an equidigital number, since it uses as much as digits as its factorization.

21900001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87502.

The product of its (nonzero) digits is 18, while the sum is 13.

The square root of 21900001 is about 4679.7436895625. The cubic root of 21900001 is about 279.7787410212.

Adding to 21900001 its reverse (10000912), we get a palindrome (31900913).

The spelling of 21900001 in words is "twenty-one million, nine hundred thousand, one".