1265521621 has 32 divisors (see below), whose sum is σ = 1622880000. Its totient is φ = 960145920.

The previous prime is 1265521583. The next prime is 1265521637. The reversal of 1265521621 is 1261255621.

It is a cyclic number.

It is not a de Polignac number, because 1265521621 - 2⁹ = 1265521109 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1265521721) 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, 217255 + ... + 223003.

It is an arithmetic number, because the mean of its divisors is an integer number (50715000).

Almost surely, 2^1265521621 is an apocalyptic number.

It is an amenable number.

1265521621 is a deficient number, since it is larger than the sum of its proper divisors (357358379).

1265521621 is a wasteful number, since it uses less digits than its factorization.

1265521621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5869.

The product of its digits is 7200, while the sum is 31.

The square root of 1265521621 is about 35574.1707001021. The cubic root of 1265521621 is about 1081.6577254090.

The spelling of 1265521621 in words is "one billion, two hundred sixty-five million, five hundred twenty-one thousand, six hundred twenty-one".