20742921 has 12 divisors (see below), whose sum is σ = 30001972. Its totient is φ = 13810176.

The previous prime is 20742919. The next prime is 20742929. The reversal of 20742921 is 12924702.

It can be written as a sum of positive squares in 2 ways, for example, as 17338896 + 3404025 = 4164^2 + 1845^2 .

It is not a de Polignac number, because 20742921 - 2¹ = 20742919 is a prime.

It is a super-2 number, since 2×20742921² = 860537543224482, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20742929) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10785 + ... + 12561.

Almost surely, 2^20742921 is an apocalyptic number.

It is an amenable number.

20742921 is a deficient number, since it is larger than the sum of its proper divisors (9259051).

20742921 is a wasteful number, since it uses less digits than its factorization.

20742921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3080 (or 3077 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 27.

The square root of 20742921 is about 4554.4397020929. The cubic root of 20742921 is about 274.7619802730.

The spelling of 20742921 in words is "twenty million, seven hundred forty-two thousand, nine hundred twenty-one".