21631427 has 4 divisors (see below), whose sum is σ = 21649056. Its totient is φ = 21613800.

The previous prime is 21631409. The next prime is 21631439. The reversal of 21631427 is 72413612.

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

It is a cyclic number.

It is not a de Polignac number, because 21631427 - 2⁸ = 21631171 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21631396 and 21631405.

It is not an unprimeable number, because it can be changed into a prime (21631447) 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, 6824 + ... + 9477.

It is an arithmetic number, because the mean of its divisors is an integer number (5412264).

Almost surely, 2^21631427 is an apocalyptic number.

21631427 is a deficient number, since it is larger than the sum of its proper divisors (17629).

21631427 is a wasteful number, since it uses less digits than its factorization.

21631427 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17628.

The product of its digits is 2016, while the sum is 26.

The square root of 21631427 is about 4650.9597934190. The cubic root of 21631427 is about 278.6303305021.

The spelling of 21631427 in words is "twenty-one million, six hundred thirty-one thousand, four hundred twenty-seven".