20021551 has 8 divisors (see below), whose sum is σ = 22432464. Its totient is φ = 17709120.

The previous prime is 20021549. The next prime is 20021623. The reversal of 20021551 is 15512002.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20021551 - 2¹ = 20021549 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 (20021501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24190 + ... + 25003.

It is an arithmetic number, because the mean of its divisors is an integer number (2804058).

Almost surely, 2^20021551 is an apocalyptic number.

20021551 is a deficient number, since it is larger than the sum of its proper divisors (2410913).

20021551 is a wasteful number, since it uses less digits than its factorization.

20021551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49241.

The product of its (nonzero) digits is 100, while the sum is 16.

The square root of 20021551 is about 4474.5447813157. The cubic root of 20021551 is about 271.5392240178.

Adding to 20021551 its reverse (15512002), we get a palindrome (35533553).

It can be divided in two parts, 2002 and 1551, that added together give a palindrome (3553).

The spelling of 20021551 in words is "twenty million, twenty-one thousand, five hundred fifty-one".