20154220021 has 4 divisors (see below), whose sum is σ = 21704544652. Its totient is φ = 18603895392.

The previous prime is 20154220003. The next prime is 20154220039. The reversal of 20154220021 is 12002245102.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12002245102 = 2 ⋅6001122551.

It is an interprime number because it is at equal distance from previous prime (20154220003) and next prime (20154220039).

It can be written as a sum of positive squares in 2 ways, for example, as 7676212996 + 12478007025 = 87614^2 + 111705^2 .

It is a cyclic number.

It is not a de Polignac number, because 20154220021 - 2⁷ = 20154219893 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20154220091) 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, 775162296 + ... + 775162321.

It is an arithmetic number, because the mean of its divisors is an integer number (5426136163).

Almost surely, 2^20154220021 is an apocalyptic number.

It is an amenable number.

20154220021 is a deficient number, since it is larger than the sum of its proper divisors (1550324631).

20154220021 is a wasteful number, since it uses less digits than its factorization.

20154220021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1550324630.

The product of its (nonzero) digits is 320, while the sum is 19.

Adding to 20154220021 its reverse (12002245102), we get a palindrome (32156465123).

The spelling of 20154220021 in words is "twenty billion, one hundred fifty-four million, two hundred twenty thousand, twenty-one".