1265721000 has 64 divisors (see below), whose sum is σ = 3949058880. Its totient is φ = 337524800.

The previous prime is 1265720999. The next prime is 1265721029. The reversal of 1265721000 is 1275621.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 207954 + ... + 213953.

It is an arithmetic number, because the mean of its divisors is an integer number (61704045).

Almost surely, 2^1265721000 is an apocalyptic number.

1265721000 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1265721000 is an abundant number, since it is smaller than the sum of its proper divisors (2683337880).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1265721000 is a wasteful number, since it uses less digits than its factorization.

1265721000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 421931 (or 421917 counting only the distinct ones).

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 1265721000 is about 35576.9728897780. The cubic root of 1265721000 is about 1081.7145263643.

Adding to 1265721000 its reverse (1275621), we get a palindrome (1266996621).

The spelling of 1265721000 in words is "one billion, two hundred sixty-five million, seven hundred twenty-one thousand".