21407221 has 8 divisors (see below), whose sum is σ = 23595264. Its totient is φ = 19259520.

The previous prime is 21407213. The next prime is 21407257. The reversal of 21407221 is 12270412.

It is a happy number.

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 21407221 - 2³ = 21407213 is a prime.

It is a super-2 number, since 2×21407221² = 916538221885682, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21407261) 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, 8965 + ... + 11098.

It is an arithmetic number, because the mean of its divisors is an integer number (2949408).

Almost surely, 2^21407221 is an apocalyptic number.

It is an amenable number.

21407221 is a deficient number, since it is larger than the sum of its proper divisors (2188043).

21407221 is a wasteful number, since it uses less digits than its factorization.

21407221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20171.

The product of its (nonzero) digits is 224, while the sum is 19.

The square root of 21407221 is about 4626.7938142952. The cubic root of 21407221 is about 277.6643335810.

Adding to 21407221 its reverse (12270412), we get a palindrome (33677633).

The spelling of 21407221 in words is "twenty-one million, four hundred seven thousand, two hundred twenty-one".