20721002 has 4 divisors (see below), whose sum is σ = 31081506. Its totient is φ = 10360500.

The previous prime is 20720971. The next prime is 20721013. The reversal of 20721002 is 20012702.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 20012702 = 2 ⋅10006351.

It can be written as a sum of positive squares in only one way, i.e., 13756681 + 6964321 = 3709^2 + 2639^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5180249 + ... + 5180252.

Almost surely, 2^20721002 is an apocalyptic number.

20721002 is a deficient number, since it is larger than the sum of its proper divisors (10360504).

20721002 is a wasteful number, since it uses less digits than its factorization.

20721002 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10360503.

The product of its (nonzero) digits is 56, while the sum is 14.

The square root of 20721002 is about 4552.0327327470. The cubic root of 20721002 is about 274.6651660327.

Adding to 20721002 its reverse (20012702), we get a palindrome (40733704).

The spelling of 20721002 in words is "twenty million, seven hundred twenty-one thousand, two".