21172401 has 16 divisors (see below), whose sum is σ = 31456320. Its totient is φ = 14074560.

The previous prime is 21172381. The next prime is 21172423. The reversal of 21172401 is 10427112.

It is not a de Polignac number, because 21172401 - 2⁵ = 21172369 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21172451) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10786 + ... + 12596.

It is an arithmetic number, because the mean of its divisors is an integer number (1966020).

Almost surely, 2^21172401 is an apocalyptic number.

It is an amenable number.

21172401 is a deficient number, since it is larger than the sum of its proper divisors (10283919).

21172401 is a wasteful number, since it uses less digits than its factorization.

21172401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2253 (or 2247 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 18.

The square root of 21172401 is about 4601.3477373483. The cubic root of 21172401 is about 276.6453471419.

Adding to 21172401 its reverse (10427112), we get a palindrome (31599513).

The spelling of 21172401 in words is "twenty-one million, one hundred seventy-two thousand, four hundred one".