721421688 has 32 divisors (see below), whose sum is σ = 1942290000. Its totient is φ = 221975808.

The previous prime is 721421681. The next prime is 721421737. The reversal of 721421688 is 886124127.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721421681) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1155813 + ... + 1156436.

Almost surely, 2^721421688 is an apocalyptic number.

721421688 is a gapful number since it is divisible by the number (78) formed by its first and last digit.

It is an amenable number.

721421688 is an abundant number, since it is smaller than the sum of its proper divisors (1220868312).

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

721421688 is a wasteful number, since it uses less digits than its factorization.

721421688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2312271 (or 2312267 counting only the distinct ones).

The product of its digits is 43008, while the sum is 39.

The square root of 721421688 is about 26859.2942572957. The cubic root of 721421688 is about 896.8704836188.

The spelling of 721421688 in words is "seven hundred twenty-one million, four hundred twenty-one thousand, six hundred eighty-eight".