621067721 has 16 divisors (see below), whose sum is σ = 643222800. Its totient is φ = 599436288.

The previous prime is 621067709. The next prime is 621067723. The reversal of 621067721 is 127760126.

It can be written as a sum of positive squares in 8 ways, for example, as 15366400 + 605701321 = 3920^2 + 24611^2 .

It is a de Polignac number, because none of the positive numbers 2^k-621067721 is a prime.

It is a super-2 number, since 2×621067721² = 771450228136267682, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (621067723) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 707735 + ... + 708611.

It is an arithmetic number, because the mean of its divisors is an integer number (40201425).

Almost surely, 2^621067721 is an apocalyptic number.

It is an amenable number.

621067721 is a deficient number, since it is larger than the sum of its proper divisors (22155079).

621067721 is a wasteful number, since it uses less digits than its factorization.

621067721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1148.

The product of its (nonzero) digits is 7056, while the sum is 32.

The square root of 621067721 is about 24921.2303267716. The cubic root of 621067721 is about 853.1911056327.

The spelling of 621067721 in words is "six hundred twenty-one million, sixty-seven thousand, seven hundred twenty-one".