20421572 has 6 divisors (see below), whose sum is σ = 35737758. Its totient is φ = 10210784.

The previous prime is 20421571. The next prime is 20421593. The reversal of 20421572 is 27512402.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 15555136 + 4866436 = 3944^2 + 2206^2 .

It is not an unprimeable number, because it can be changed into a prime (20421571) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2552693 + ... + 2552700.

It is an arithmetic number, because the mean of its divisors is an integer number (5956293).

Almost surely, 2^20421572 is an apocalyptic number.

It is an amenable number.

20421572 is a deficient number, since it is larger than the sum of its proper divisors (15316186).

20421572 is a wasteful number, since it uses less digits than its factorization.

20421572 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5105397 (or 5105395 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 23.

The square root of 20421572 is about 4519.0233458127. The cubic root of 20421572 is about 273.3357201193.

Adding to 20421572 its reverse (27512402), we get a palindrome (47933974).

The spelling of 20421572 in words is "twenty million, four hundred twenty-one thousand, five hundred seventy-two".