21630401 has 4 divisors (see below), whose sum is σ = 23294292. Its totient is φ = 19966512.

The previous prime is 21630391. The next prime is 21630421. The reversal of 21630401 is 10403612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8271376 + 13359025 = 2876^2 + 3655^2 .

It is a cyclic number.

It is not a de Polignac number, because 21630401 - 2⁶ = 21630337 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21630401.

It is not an unprimeable number, because it can be changed into a prime (21630421) 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, 831926 + ... + 831951.

It is an arithmetic number, because the mean of its divisors is an integer number (5823573).

Almost surely, 2^21630401 is an apocalyptic number.

It is an amenable number.

21630401 is a deficient number, since it is larger than the sum of its proper divisors (1663891).

21630401 is a wasteful number, since it uses less digits than its factorization.

21630401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1663890.

The product of its (nonzero) digits is 144, while the sum is 17.

The square root of 21630401 is about 4650.8494922971. The cubic root of 21630401 is about 278.6259251949.

The spelling of 21630401 in words is "twenty-one million, six hundred thirty thousand, four hundred one".