21020031551 has 8 divisors (see below), whose sum is σ = 21333718224. Its totient is φ = 20708516160.

The previous prime is 21020031547. The next prime is 21020031581. The reversal of 21020031551 is 15513002012.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21020031551 - 2² = 21020031547 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 (21020031581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 523310 + ... + 562043.

It is an arithmetic number, because the mean of its divisors is an integer number (2666714778).

Almost surely, 2^21020031551 is an apocalyptic number.

21020031551 is a deficient number, since it is larger than the sum of its proper divisors (313686673).

21020031551 is a wasteful number, since it uses less digits than its factorization.

21020031551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1085641.

The product of its (nonzero) digits is 300, while the sum is 20.

Adding to 21020031551 its reverse (15513002012), we get a palindrome (36533033563).

The spelling of 21020031551 in words is "twenty-one billion, twenty million, thirty-one thousand, five hundred fifty-one".