1656699981 has 4 divisors (see below), whose sum is σ = 2208933312. Its totient is φ = 1104466652.

The previous prime is 1656699977. The next prime is 1656699983. The reversal of 1656699981 is 1899966561.

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 1656699981 - 2² = 1656699977 is a prime.

It is a super-2 number, since 2×1656699981² = 5489309654090800722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1656699983) 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, 276116661 + ... + 276116666.

It is an arithmetic number, because the mean of its divisors is an integer number (552233328).

Almost surely, 2^1656699981 is an apocalyptic number.

It is an amenable number.

1656699981 is a deficient number, since it is larger than the sum of its proper divisors (552233331).

1656699981 is an equidigital number, since it uses as much as digits as its factorization.

1656699981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 552233330.

The product of its digits is 6298560, while the sum is 60.

The square root of 1656699981 is about 40702.5795374200. The cubic root of 1656699981 is about 1183.2630123038.

The spelling of 1656699981 in words is "one billion, six hundred fifty-six million, six hundred ninety-nine thousand, nine hundred eighty-one".