221420021 has 4 divisors (see below), whose sum is σ = 221548512. Its totient is φ = 221291532.

The previous prime is 221420009. The next prime is 221420033. The reversal of 221420021 is 120024122.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 120024122 = 2 ⋅60012061.

It is an interprime number because it is at equal distance from previous prime (221420009) and next prime (221420033).

It is a cyclic number.

It is not a de Polignac number, because 221420021 - 2¹⁸ = 221157877 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 221419978 and 221420005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221420041) 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, 61625 + ... + 65118.

It is an arithmetic number, because the mean of its divisors is an integer number (55387128).

Almost surely, 2^221420021 is an apocalyptic number.

It is an amenable number.

221420021 is a deficient number, since it is larger than the sum of its proper divisors (128491).

221420021 is a wasteful number, since it uses less digits than its factorization.

221420021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128490.

The product of its (nonzero) digits is 64, while the sum is 14.

The square root of 221420021 is about 14880.1888764894. The cubic root of 221420021 is about 604.9771373097.

Adding to 221420021 its reverse (120024122), we get a palindrome (341444143).

The spelling of 221420021 in words is "two hundred twenty-one million, four hundred twenty thousand, twenty-one".