63649981 has 4 divisors (see below), whose sum is σ = 67000000. Its totient is φ = 60299964.

The previous prime is 63649931. The next prime is 63649991. The reversal of 63649981 is 18994636.

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 a cyclic number.

It is not a de Polignac number, because 63649981 - 2¹³ = 63641789 is a prime.

It is a super-2 number, since 2×63649981² = 8102640162600722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (63649931) 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, 1674981 + ... + 1675018.

It is an arithmetic number, because the mean of its divisors is an integer number (16750000).

Almost surely, 2^63649981 is an apocalyptic number.

It is an amenable number.

63649981 is a deficient number, since it is larger than the sum of its proper divisors (3350019).

63649981 is a wasteful number, since it uses less digits than its factorization.

63649981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3350018.

The product of its digits is 279936, while the sum is 46.

The square root of 63649981 is about 7978.0938199547. The cubic root of 63649981 is about 399.2694603418.

The spelling of 63649981 in words is "sixty-three million, six hundred forty-nine thousand, nine hundred eighty-one".