6401981 has 4 divisors (see below), whose sum is σ = 6680352. Its totient is φ = 6123612.

The previous prime is 6401977. The next prime is 6401987. The reversal of 6401981 is 1891046.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 6401981 - 2² = 6401977 is a prime.

It is a super-2 number, since 2×6401981² = 81970721448722, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6401987) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 139151 + ... + 139196.

It is an arithmetic number, because the mean of its divisors is an integer number (1670088).

Almost surely, 2^6401981 is an apocalyptic number.

It is an amenable number.

6401981 is a deficient number, since it is larger than the sum of its proper divisors (278371).

6401981 is a wasteful number, since it uses less digits than its factorization.

6401981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 278370.

The product of its (nonzero) digits is 1728, while the sum is 29.

The square root of 6401981 is about 2530.2136273445. The cubic root of 6401981 is about 185.6827075923.

The spelling of 6401981 in words is "six million, four hundred one thousand, nine hundred eighty-one".