1021720851 has 32 divisors (see below), whose sum is σ = 1534982400. Its totient is φ = 671616000.

The previous prime is 1021720783. The next prime is 1021720853. The reversal of 1021720851 is 1580271201.

It is not a de Polignac number, because 1021720851 - 2⁹ = 1021720339 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (1021720853) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 724435 + ... + 725843.

It is an arithmetic number, because the mean of its divisors is an integer number (47968200).

Almost surely, 2^1021720851 is an apocalyptic number.

1021720851 is a deficient number, since it is larger than the sum of its proper divisors (513261549).

1021720851 is a wasteful number, since it uses less digits than its factorization.

1021720851 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1776 (or 1770 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 27.

The square root of 1021720851 is about 31964.3684592704. The cubic root of 1021720851 is about 1007.1884855225.

The spelling of 1021720851 in words is "one billion, twenty-one million, seven hundred twenty thousand, eight hundred fifty-one".