21072401 has 24 divisors (see below), whose sum is σ = 26630856. Its totient is φ = 16558080.

The previous prime is 21072379. The next prime is 21072407. The reversal of 21072401 is 10427012.

It can be written as a sum of positive squares in 4 ways, for example, as 50176 + 21022225 = 224^2 + 4585^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21072401 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (17).

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 21072401.

It is not an unprimeable number, because it can be changed into a prime (21072407) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 33845 + ... + 34461.

It is an arithmetic number, because the mean of its divisors is an integer number (1109619).

Almost surely, 2^21072401 is an apocalyptic number.

It is an amenable number.

21072401 is a deficient number, since it is larger than the sum of its proper divisors (5558455).

21072401 is a wasteful number, since it uses less digits than its factorization.

21072401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 689 (or 682 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 17.

The square root of 21072401 is about 4590.4684946092. The cubic root of 21072401 is about 276.2091156574.

Adding to 21072401 its reverse (10427012), we get a palindrome (31499413).

The spelling of 21072401 in words is "twenty-one million, seventy-two thousand, four hundred one".