20021261 has 10 divisors (see below), whose sum is σ = 21720582. Its totient is φ = 18454800.

The previous prime is 20021251. The next prime is 20021263. The reversal of 20021261 is 16212002.

It can be written as a sum of positive squares in 5 ways, for example, as 13645636 + 6375625 = 3694^2 + 2525^2 .

It is a de Polignac number, because none of the positive numbers 2^k-20021261 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20021263) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 28211 + ... + 28911.

Almost surely, 2^20021261 is an apocalyptic number.

It is an amenable number.

20021261 is a deficient number, since it is larger than the sum of its proper divisors (1699321).

20021261 is an frugal number, since it uses more digits than its factorization.

20021261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 753 (or 714 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 20021261 is about 4474.5123756673. The cubic root of 20021261 is about 271.5379129846.

Adding to 20021261 its reverse (16212002), we get a palindrome (36233263).

The spelling of 20021261 in words is "twenty million, twenty-one thousand, two hundred sixty-one".