1640737721 has 8 divisors (see below), whose sum is σ = 1875783744. Its totient is φ = 1405855440.

The previous prime is 1640737717. The next prime is 1640737781. The reversal of 1640737721 is 1277370461.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1640737721 - 2² = 1640737717 is a prime.

It is a super-2 number, since 2×1640737721² = 5384040538224547682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1640737781) 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, 18650 + ... + 60243.

It is an arithmetic number, because the mean of its divisors is an integer number (234472968).

Almost surely, 2^1640737721 is an apocalyptic number.

It is an amenable number.

1640737721 is a deficient number, since it is larger than the sum of its proper divisors (235046023).

1640737721 is an equidigital number, since it uses as much as digits as its factorization.

1640737721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81871.

The product of its (nonzero) digits is 49392, while the sum is 38.

The square root of 1640737721 is about 40506.0207993824. The cubic root of 1640737721 is about 1179.4505056698.

The spelling of 1640737721 in words is "one billion, six hundred forty million, seven hundred thirty-seven thousand, seven hundred twenty-one".