21531401 has 8 divisors (see below), whose sum is σ = 23185440. Its totient is φ = 19920448.

The previous prime is 21531379. The next prime is 21531439. The reversal of 21531401 is 10413512.

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

It is a cyclic number.

It is not a de Polignac number, because 21531401 - 2⁶ = 21531337 is a prime.

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

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21531401.

It is not an unprimeable number, because it can be changed into a prime (21531481) 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, 9731 + ... + 11736.

It is an arithmetic number, because the mean of its divisors is an integer number (2898180).

Almost surely, 2^21531401 is an apocalyptic number.

It is an amenable number.

21531401 is a deficient number, since it is larger than the sum of its proper divisors (1654039).

21531401 is a wasteful number, since it uses less digits than its factorization.

21531401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21543.

The product of its (nonzero) digits is 120, while the sum is 17.

The square root of 21531401 is about 4640.1940692174. The cubic root of 21531401 is about 278.2001948094.

Adding to 21531401 its reverse (10413512), we get a palindrome (31944913).

The spelling of 21531401 in words is "twenty-one million, five hundred thirty-one thousand, four hundred one".