31821921769 has 9 divisors (see below), whose sum is σ = 34979971831. Its totient is φ = 28927235920.

The previous prime is 31821921709. The next prime is 31821921797. The reversal of 31821921769 is 96712912813.

It is a happy number.

The square root of 31821921769 is 178387.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 25563213225 + 6258708544 = 159885^2 + 79112^2 .

It is not a de Polignac number, because 31821921769 - 2⁷ = 31821921641 is a prime.

It is a super-2 number, since 2×31821921769² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31821921709) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1954149 + ... + 1970365.

Almost surely, 2^31821921769 is an apocalyptic number.

31821921769 is the 178387-th square number.

31821921769 is the 89194-th centered octagonal number.

It is an amenable number.

31821921769 is a deficient number, since it is larger than the sum of its proper divisors (3158050062).

31821921769 is an frugal number, since it uses more digits than its factorization.

31821921769 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32456 (or 16228 counting only the distinct ones).

The product of its digits is 326592, while the sum is 49.

Multiplying 31821921769 by its sum of digits (49), we get a square (1559274166681 = 1248709²).

The spelling of 31821921769 in words is "thirty-one billion, eight hundred twenty-one million, nine hundred twenty-one thousand, seven hundred sixty-nine".