1213755921 has 75 divisors (see below), whose sum is σ = 2142319641. Its totient is φ = 684795384.

The previous prime is 1213755901. The next prime is 1213755947. The reversal of 1213755921 is 1295573121.

The square root of 1213755921 is 34839.

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

It is not a de Polignac number, because 1213755921 - 2¹³ = 1213747729 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1213755901) 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 74 ways as a sum of consecutive naturals, for example, 15363960 + ... + 15364038.

Almost surely, 2^1213755921 is an apocalyptic number.

1213755921 is the 34839-th square number.

1213755921 is the 17420-th centered octagonal number.

It is an amenable number.

1213755921 is a deficient number, since it is larger than the sum of its proper divisors (928563720).

1213755921 is an frugal number, since it uses more digits than its factorization.

1213755921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 198 (or 89 counting only the distinct ones).

The product of its digits is 18900, while the sum is 36.

The cubic root of 1213755921 is about 1066.7036648083.

Multiplying 1213755921 by its sum of digits (36), we get a square (43695213156 = 209034²).

The spelling of 1213755921 in words is "one billion, two hundred thirteen million, seven hundred fifty-five thousand, nine hundred twenty-one".